Examkin

All practice questions

4736 questions

All types4,736Multiple choice2,413Multiple select567Numeric127Matching858Ordering771
Question 801Question →

An otherwise healthy 24-year-old female visits her physician complaining of a new lump in her left breast that she noticed two weeks ago while showering. She has no personal or family history of breast cancer and reports no nipple discharge, overlying skin changes, or systemic symptoms. Her menstrual cycles are regular. Vital signs are within normal limits. On physical examination, a 2-cm, firm, mobile, well-circumscribed, non-tender mass is palpated in the upper outer quadrant of the left breast. There is no axillary lymphadenopathy, and examination of the right breast is unremarkable. Which of the following is the most appropriate next step in the diagnostic workup for this patient?

Show answer & explanation

Answer: Targeted ultrasound of the left breast

Answer

Targeted ultrasound of the left breast
Targeted breast ultrasound is the most appropriate next step in management. The patient is under 30 years of age with a palpable breast mass. In this age demographic, breast tissue is predominantly radiodense (glandular), which significantly reduces the sensitivity of mammography. Ultrasound is highly sensitive for distinguishing between solid and cystic structures, can accurately characterize the mass, and does not expose the young patient to ionizing radiation.

Step-by-Step Solution

1
Identify the patient's demographic profile and chief complaint.
The patient is a 24-year-old female presenting with a new, palpable, distinct breast mass.
Age is the primary determinant for the sequencing of imaging modalities in the workup of breast lesions.
2
Evaluate the clinical features of the mass.
The mass is firm, mobile, and well-circumscribed, which clinically suggests a benign etiology such as a fibroadenoma.
Although the features are benign, clinical examination alone is insufficient to definitively rule out malignancy.
3
Determine the initial guideline-supported diagnostic test.
Targeted ultrasound is selected over mammography.
In women under 30, breast tissue is typically dense, which significantly limits the sensitivity of a mammogram. Ultrasound effectively differentiates solid from cystic lesions without exposing the young patient to ionizing radiation.

Key Concept

In women younger than 30 years of age presenting with a new palpable breast mass, targeted breast ultrasound is the initial imaging modality of choice due to dense breast tissue and the goal of avoiding ionizing radiation.
Question 802Question →

During morning rounds on the inpatient medical ward, a physician is urgently called to evaluate a patient who developed new-onset bilateral lower extremity weakness and urinary incontinence overnight. The patient was admitted three days ago for methicillin-resistant *Staphylococcus aureus* bacteremia secondary to an infected foot ulcer. His temperature is 38.8∘C38.8^\circ\text{C} (101.8∘F101.8^\circ\text{F}). Neurologic examination reveals 2/52/5 motor strength in the bilateral lower extremities, absent patellar and Achilles reflexes, and markedly decreased rectal sphincter tone. Palpation of the lower back elicits exquisite focal tenderness over the L4 spinous process. The patient's past medical history is notable for severe ischemic cardiomyopathy, for which a dual-chamber permanent pacemaker was placed 1212 years ago. Medical records confirm the implanted device is a legacy model that is not MRI-conditional. Which of the following is the most appropriate next step in imaging this patient?

Show answer & explanation

Answer: Computed tomography (CT) myelography of the spine

Answer

Computed tomography (CT) myelography of the spine
The clinical presentation (fever, focal back pain, and progressive neurologic deficits including bowel and bladder dysfunction) in a patient with MRSA bacteremia is highly suspicious for a spinal epidural abscess causing cauda equina syndrome. This is a neurologic emergency requiring urgent decompression. While magnetic resonance imaging (MRI) of the spine with contrast is the gold standard diagnostic test, this patient has an absolute contraindication to MRI due to a legacy (non-MRI-conditional) permanent pacemaker. In patients who cannot undergo MRI, computed tomography (CT) myelography is the imaging modality of choice. It involves the injection of contrast dye into the subarachnoid space followed by CT scanning, providing excellent visualization of the spinal cord, nerve roots, and any extrinsic compression by an epidural mass.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has fever, focal back pain, and progressive neurologic deficits (lower extremity weakness, urinary incontinence, decreased rectal tone) in the setting of MRSA bacteremia.
This classic triad combined with a known hematogenous source highly suggests a spinal epidural abscess (SEA) causing cauda equina syndrome.
2
Determine the gold-standard diagnostic imaging.
Urgent MRI of the spine with and without contrast is typically required to visualize the epidural space and extent of neural compression.
MRI provides the best soft-tissue resolution of the spinal cord and surrounding structures.
3
Assess the patient for contraindications to the preferred imaging.
The patient has a 12-year-old legacy (non-MRI-conditional) permanent pacemaker.
Subjecting this device to the strong magnetic fields of an MRI can cause device malfunction, heating, or dislodgement, making MRI absolutely contraindicated.
4
Select the best alternative imaging modality.
CT myelography of the spine is chosen.
It involves the injection of intrathecal contrast followed by a CT scan, providing the necessary detailed visualization of the spinal canal to diagnose an epidural abscess when MRI cannot be performed.

Key Concept

Alternative imaging modalities for spinal cord emergencies in patients with MRI contraindications
Question 803Question →

A previously healthy 4242-year-old man visits a new primary care provider to establish medical care. He reports feeling unusually fatigued over the last few months, accompanied by frequent muscle cramps in his legs and an increase in nighttime urination. He has not seen a physician in five years and currently takes no medications. His blood pressure is 172/104172/104 mmHg, and his heart rate is 7878/min. Physical examination reveals normal heart sounds, clear lungs, and no abdominal bruits. Laboratory testing shows the following:

TestValue
Sodium145145 mEq/L
Potassium2.82.8 mEq/L
Chloride102102 mEq/L
Bicarbonate3131 mEq/L
Creatinine0.90.9 mg/dL

Which of the following is the most appropriate next step in the diagnostic evaluation of this patient?

Show answer & explanation

Answer: Measurement of plasma aldosterone-to-renin ratio

Answer

Measurement of plasma aldosterone-to-renin ratio
The correct answer is measurement of the plasma aldosterone-to-renin ratio. This patient presents with the classic triad of primary hyperaldosteronism: severe hypertension, spontaneous hypokalemia, and metabolic alkalosis. The Endocrine Society guidelines mandate a strict stepwise diagnostic approach. The first step is always biochemical screening using the plasma aldosterone concentration (PAC) to plasma renin activity (PRA) ratio. A high ratio (typically > 2020) with an elevated PAC (> 1515 ng/dL) suggests autonomous aldosterone production (primary hyperaldosteronism), while a low ratio suggests secondary hyperaldosteronism (e.g., renal artery stenosis).

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's presentation and laboratory results.
The patient presents with severe hypertension, spontaneous hypokalemia (2.82.8 mEq/L), and metabolic alkalosis (bicarbonate 3131 mEq/L) in the absence of diuretic use.
Recognizing this classic triad is essential to formulate a differential diagnosis that prioritizes hyperaldosteronism.
2
Determine the initial diagnostic priority for the suspected condition.
The clinician must differentiate between primary hyperaldosteronism (Conn syndrome) and secondary hyperaldosteronism (e.g., renal artery stenosis).
These etiologies require fundamentally different downstream testing and management algorithms.
3
Select the appropriate guideline-recommended initial test.
The plasma aldosterone-to-renin ratio (ARR) is chosen as the first step.
The ARR is the most reliable, non-invasive first-line screening tool to establish the biochemical presence of primary hyperaldosteronism.

Key Concept

The initial step in evaluating suspected primary hyperaldosteronism (suggested by hypertension, hypokalemia, and metabolic alkalosis) is biochemical screening with the plasma aldosterone-to-renin ratio.
Question 804Question →

A 58-year-old woman is referred to a general surgeon after a routine screening mammogram demonstrated an area of architectural distortion in the left breast. She has no palpable breast masses, nipple discharge, or overlying skin changes. A core needle biopsy of the abnormal area is performed. The pathology report indicates an invasive breast malignancy characterized by a complete loss of E-cadherin expression due to a mutation in the CDH1 gene. Based on this molecular profile, which of the following histopathologic findings is most likely present on the biopsy specimen?

Show answer & explanation

Answer: Small, monomorphic cells infiltrating the stroma in a single-file linear pattern

Answer

Small, monomorphic cells infiltrating the stroma in a single-file linear pattern
The correct answer accurately describes the pathognomonic histology of invasive lobular carcinoma (ILC). The loss of E-cadherin, a cell surface protein responsible for intercellular adhesion encoded by the CDH1 gene, causes the neoplastic cells to lose their cohesiveness. Consequently, they do not form glands or ducts. Instead, they infiltrate the breast stroma individually or in classic linear cords, commonly referred to as a 'single-file' pattern.

Step-by-Step Solution

1
Analyze the biopsy's molecular profile provided in the stem.
The biopsy shows a loss of E-cadherin expression due to a CDH1 gene mutation.
Identifying the molecular driver is key to determining the histologic subtype of breast cancer.
2
Correlate the molecular finding with a specific breast cancer diagnosis.
Loss of E-cadherin is the hallmark of Invasive Lobular Carcinoma (ILC).
E-cadherin is an intercellular adhesion molecule; its absence is characteristic of lobular, rather than ductal, carcinomas.
3
Determine the expected histopathologic appearance of the diagnosed cancer.
ILC appears as small, monomorphic cells infiltrating in a single-file pattern.
Because the cells lack E-cadherin, they cannot stick together to form glands or sheets, leading to the classic single-file linear cord histology.

Key Concept

Correlation of E-cadherin loss (CDH1 mutation) with the single-file histologic pattern of Invasive Lobular Carcinoma.
Question 805Question →

A 71-year-old female resident of a skilled nursing facility is brought to the emergency department due to profound lethargy. Staff report she has been increasingly confused since yesterday. Her temperature is 39.5°C (103.1°F), blood pressure is 78/42 mm Hg, heart rate is 134/min, and respiratory rate is 24/min. Pulse oximetry shows 95% on room air. Physical examination reveals warm, flushed extremities, dry mucous membranes, and cloudy, malodorous urine in her collection bag. Which of the following simultaneous initial emergency orders are most appropriate? (Select all that apply)

Select all that apply

Show answer & explanation

Answer: Provide a rapid intravenous bolus of isotonic crystalloid.; Draw peripheral blood cultures and administer empiric broad-spectrum antibiotics.

Answer

The correct simultaneous initial emergency orders are to provide a rapid intravenous bolus of isotonic crystalloid, draw peripheral blood cultures, and administer empiric broad-spectrum antibiotics.
This patient presents in septic shock, likely secondary to a severe urinary tract infection. The initial stabilization of septic shock requires immediate and simultaneous interventions focused on restoring tissue perfusion and targeting the infection. This includes a rapid bolus of isotonic crystalloids (typically 30 mL/kg) to correct hypovolemia from vasodilation and capillary leak. Concurrently, blood cultures must be drawn, followed immediately by the administration of empiric broad-spectrum antibiotics. These steps are standard components of the initial sepsis bundle and significantly reduce mortality when executed promptly.

Step-by-Step Solution

1
Identify the clinical syndrome.
The patient's fever, hypotension, tachycardia, altered mental status, and likely urinary source indicate septic shock.
Recognizing the etiology of shock guides the immediate resuscitation priorities.
2
Prioritize initial stabilization interventions.
The immediate focus must be on restoring perfusion and treating the underlying infection simultaneously.
In distributive shock caused by sepsis, the intravascular space is depleted, requiring immediate volume expansion and source control.
3
Select the appropriate orders.
Isotonic crystalloids are ordered for volume expansion, and blood cultures are drawn immediately prior to administering broad-spectrum antibiotics.
This aligns with evidence-based initial sepsis bundles to reduce mortality.

Key Concept

Initial stabilization of septic shock requires simultaneous administration of rapid isotonic crystalloid fluids, obtaining blood cultures, and initiating broad-spectrum antibiotics within the first hour.
Estimated Time:1m 15s
Question 806Question →

A 61-year-old man presents to the outpatient clinic for the evaluation of a right foot wound. He has a 15-year history of poorly controlled type 2 diabetes mellitus, hypertension, and severe peripheral neuropathy. The patient states he first noticed a painless sore on the bottom of his right big toe approximately two weeks ago. He has experienced no fevers, chills, or systemic symptoms. Vital signs are within normal limits. Physical examination reveals a 1.5-cm, deep ulceration on the plantar aspect of the right first metatarsophalangeal joint. There is a 2-mm rim of surrounding erythema, but no fluctuance or purulent drainage is noted. During the examination, a sterile metal probe is inserted into the ulcer and touches hard, gritty tissue at the base of the wound. Laboratory studies show a leukocyte count of 8,500/mm38,500/mm^3 and an erythrocyte sedimentation rate of 68 mm/h68 \text{ mm/h}. Which of the following is the most appropriate initial imaging study to order for this patient?

Show answer & explanation

Answer: Plain radiography of the right foot

Answer

Plain radiography of the right foot
The correct answer is plain radiography. In any patient with a diabetic foot ulcer and a high suspicion for osteomyelitis (strongly suggested here by the positive probe-to-bone test and elevated erythrocyte sedimentation rate), plain radiography of the foot is the mandatory initial imaging study. Although it has low sensitivity for acute osteomyelitis (often requiring 10-14 days for cortical destruction or periosteal reaction to become visible), it is highly cost-effective, easily accessible, and essential for ruling out other causes of foot pain or deformity, such as Charcot arthropathy, soft tissue gas, or radio-opaque foreign bodies.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and physical examination findings.
The patient has a deep diabetic foot ulcer with a positive probe-to-bone test and an elevated erythrocyte sedimentation rate.
Identifying these key features raises the clinical suspicion for contiguous osteomyelitis.
2
Determine the standard diagnostic sequencing for the suspected condition.
Guidelines dictate that all patients with suspected osteomyelitis should initially undergo plain radiography of the affected area.
Plain films are inexpensive, readily available, and can identify alternative diagnoses or severe bone destruction, serving as a baseline before advancing to more expensive imaging.
3
Evaluate the roles of advanced imaging modalities.
Advanced imaging (like magnetic resonance imaging) is deferred unless initial radiographs are negative or surgical intervention is being planned.
To prevent the overutilization of healthcare resources and adhere to correct step-wise diagnostic protocols.

Key Concept

In patients with suspected osteomyelitis (e.g., a diabetic foot ulcer with a positive probe-to-bone test), plain radiography is always the most appropriate initial imaging study.
Question 807Question →

A 64-year-old man is evaluated in the emergency department for a 5-day history of progressively worsening, severe mid-back pain. He describes the pain as a dull, constant ache that is not relieved by position changes or over-the-counter analgesics. Over the past 12 hours, he has developed bilateral leg heaviness and difficulty initiating micturition. His medical history is significant for type 2 diabetes mellitus, hypertension, and a recent episode of methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia secondary to a peripheral intravenous catheter infection 3 weeks ago. He completed a 14-day course of oral cephalexin for the bacteremia. His temperature is 38.2°C (100.8°F), blood pressure is 145/88 mmHg, and pulse is 98/min. Physical examination reveals focal tenderness to percussion over the T8-T10 spinous processes. Neurological examination demonstrates 4/5 strength in the bilateral lower extremities, diminished deep tendon reflexes at the knees and ankles, and decreased sensation to pinprick below the umbilicus. A bladder scan shows a post-void residual volume of 450 mL.

Which of the following diagnostic steps should be prioritized and performed concurrently in this patient's initial evaluation? (Select 2)

Select all that apply

Show answer & explanation

Answer: Magnetic resonance imaging of the entire spine with and without intravenous contrast; Two sets of peripheral blood cultures

Answer

The correct diagnostic steps to perform concurrently are magnetic resonance imaging of the entire spine with and without intravenous contrast, and obtaining two sets of peripheral blood cultures.
The correct diagnostic steps are magnetic resonance imaging (MRI) of the entire spine with contrast and two sets of peripheral blood cultures. This patient's presentation of fever, severe focal back pain, and acute neurological deficits (paraparesis, sensory level, urinary retention) in the setting of recent staphylococcal bacteremia is highly suspicious for a spinal epidural abscess (SEA). SEA is a life-threatening neurological emergency. MRI of the entire spine with and without contrast is the definitive imaging modality of choice due to its superior soft-tissue resolution, which allows for precise localization of the abscess and evaluation of spinal cord compression. The entire spine should be imaged because up to 15% of patients with SEA have noncontiguous 'skip' lesions. Concurrently, two sets of peripheral blood cultures must be drawn prior to the administration of empiric broad-spectrum antibiotics. Blood cultures are positive in over 60% of SEA cases and are crucial for identifying the causative pathogen (most commonly Staphylococcus aureus) and tailoring long-term antimicrobial therapy.

Step-by-Step Solution

1
Identify the clinical syndrome based on the classic triad of symptoms and signs.
The patient presents with focal back pain, fever, and new-onset neurological deficits (lower extremity weakness, sensory loss, urinary retention with high post-void residual), which is the classic presentation for a spinal epidural abscess (SEA).
Recognizing this triad is essential because SEA is a neurological emergency requiring rapid diagnosis and intervention to prevent irreversible paralysis.
2
Recognize the predisposing risk factors.
The patient has a history of type 2 diabetes mellitus and recent MSSA bacteremia, both of which significantly increase the risk for hematogenous seeding to the epidural space.
Identifying these risk factors strongly increases the pre-test probability of SEA, dictating the urgency of the diagnostic workup.
3
Select the definitive concurrent diagnostic studies.
The patient requires urgent Magnetic Resonance Imaging (MRI) of the entire spine with contrast to confirm the anatomical location and extent of the abscess, concurrently with two sets of peripheral blood cultures to identify the causative organism.
MRI is the gold standard for visualizing soft tissue infections in the epidural space. Blood cultures must be obtained before initiating empiric antibiotics to guide targeted antimicrobial therapy, as hematogenous spread is the most common etiology.

Key Concept

The initial evaluation of a suspected spinal epidural abscess requires urgent magnetic resonance imaging (MRI) of the spine with contrast to assess structural compromise, concurrently with peripheral blood cultures to establish a microbiologic diagnosis before starting empiric antibiotics.
Estimated Time:2m 0s
Question 808Question →

A physician is reviewing several skin biopsy reports from different patients evaluated in an outpatient dermatology clinic. To finalize the clinical assessments, identify the correct condition for each microscopic finding. Match each classic histopathological description to its most accurate definitive diagnosis.

Click a left item, then click its matching right item

Items

Basal cell carcinoma
Squamous cell carcinoma
Melanoma
Psoriasis
Bullous pemphigoid

Matches

Show answer & explanation

Answer

Basal cell carcinoma matches with peripheral palisading and clefting. Squamous cell carcinoma matches with intercellular bridges and keratin pearls. Melanoma matches with asymmetric proliferation and pagetoid spread. Psoriasis matches with elongated rete ridges and neutrophils in the stratum corneum. Bullous pemphigoid matches with subepidermal blisters and an eosinophil-rich infiltrate.
Definitive diagnosis in dermatology heavily relies on correlating clinical morphology with microscopic biopsy findings. Basal cell carcinoma uniquely features basaloid nests with peripheral palisading. Squamous cell carcinoma shows invasive atypical keratinocytes with keratin pearl formation. Melanoma is identified by asymmetric, atypical melanocytic proliferation with upward epidermal (pagetoid) spread. Psoriasis displays uniform epidermal hyperplasia (elongated rete ridges) and collections of neutrophils. Bullous pemphigoid is characterized by full-thickness epidermal separation (subepidermal blister) packed with eosinophils.

Step-by-Step Solution

1
Analyze the first biopsy description for key cellular architectural patterns.
Identify 'peripheral palisading' and 'clefting' as the pathognomonic features of basal cell carcinoma.
These specific architectural features distinguish basal cell carcinoma from other skin neoplasms.
2
Evaluate the descriptions highlighting keratinocytes versus melanocytes.
Keratin pearls indicate squamous cell carcinoma, while pagetoid spread of pigment-producing cells indicates melanoma.
Cell lineage specific markers (keratinization vs. melanin/pagetoid spread) differentiate the major types of skin malignancies.
3
Differentiate between the inflammatory skin condition descriptions.
Elongated rete ridges match the chronic inflammatory plaque state of psoriasis, whereas a subepidermal cleavage plane matches the autoimmune blistering mechanism of bullous pemphigoid.
Understanding the mechanism of disease (epidermal hyperproliferation vs. basement membrane antibody attack) directly correlates with the histologic findings.

Key Concept

Histopathological hallmarks of common dermatologic diseases and cutaneous malignancies.
Question 809Question →

Match each interstitial and diffuse parenchymal lung disease with its most characteristic high-resolution computed tomography (HRCT) imaging pattern.

Click a left item, then click its matching right item

Items

Idiopathic pulmonary fibrosis
Idiopathic nonspecific interstitial pneumonia
Cryptogenic organizing pneumonia
Fibrotic hypersensitivity pneumonitis
Pulmonary alveolar proteinosis

Matches

Show answer & explanation

Answer

Idiopathic pulmonary fibrosis matches with basal/subpleural honeycombing and reticular opacities. Idiopathic nonspecific interstitial pneumonia matches with basilar ground-glass opacities and subpleural sparing. Cryptogenic organizing pneumonia matches with patchy peripheral consolidation and the reverse halo sign. Fibrotic hypersensitivity pneumonitis matches with upper/mid-lung fibrosis, centrilobular micronodules, and mosaic attenuation. Pulmonary alveolar proteinosis matches with the crazy-paving pattern.
The correct pairings rely on recognizing the standardized radiologic criteria for interstitial lung diseases. Idiopathic pulmonary fibrosis requires a Usual Interstitial Pneumonia (UIP) pattern, identified by honeycombing and subpleural/basal predominance. NSIP lacks honeycombing, features uniform ground-glass opacities, and often spares the immediate subpleura. Fibrotic hypersensitivity pneumonitis is distinguished by its 'three-density pattern' (headcheese sign) and upper-lung predominance. COP presents with consolidative changes, often migrating, with the reverse halo sign. PAP is the classic cause of the extensive crazy-paving pattern without fibrosis.

Step-by-Step Solution

1
Analyze the imaging description for characteristic spatial distribution (e.g., upper vs. lower lobe, subpleural vs. peribronchovascular).
Lower lobe predominance aligns with idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP), while upper lobe points toward fibrotic hypersensitivity pneumonitis (FHP).
Spatial distribution serves as a primary discriminator in HRCT interpretation for diffuse parenchymal lung diseases.
2
Identify pathognomonic radiological signs within each description to confirm the diagnosis.
Honeycombing confirms IPF; subpleural sparing confirms NSIP; a reverse halo sign confirms cryptogenic organizing pneumonia (COP); mosaic attenuation with centrilobular nodules confirms FHP; crazy-paving confirms pulmonary alveolar proteinosis (PAP).
Specific radiological signs accurately link the descriptive text to the underlying histopathological patterns, averting the need for surgical biopsy in typical cases.

Key Concept

High-Resolution Computed Tomography (HRCT) patterns are highly specific for differentiating various diffuse parenchymal and interstitial lung diseases based on spatial distribution and pathognomonic parenchymal signs.
Estimated Time:2m 0s
Question 810Question →

A 68-year-old man with a history of ischemic cardiomyopathy presents to the emergency department with progressively worsening dyspnea. The attending physician reviews the pathophysiology of acute decompensated heart failure with the team. Arrange the following classic chest radiograph findings in the chronological sequence they typically appear as pulmonary capillary wedge pressure (PCWP) progressively increases from a normal baseline to a severely elevated state.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence tracking increasing wedge pressure is: Normal vascular distribution, followed by Cephalization, followed by Interstitial edema, and finally Alveolar edema.
The sequence perfectly tracks the pathophysiological cascade of cardiogenic pulmonary edema driven by progressively increasing hydrostatic pressure. Normal gravity-dependent flow is altered first (cephalization), followed by fluid leaking into the supportive tissue framework (interstitial edema), and concluding with fluid filling the actual airspaces (alveolar edema).

Step-by-Step Solution

1
Identify the baseline normal state of pulmonary vasculature on a chest radiograph.
Normal distribution shows larger vessels in the lower lung zones due to gravitational effects on blood flow.
Establishing the normal baseline is required to identify subsequent pathologic changes.
2
Determine the first radiographic sign of mild pulmonary venous hypertension.
Cephalization occurs as blood flow redistributes to the upper lobes when pressures reach 13-18 mmHg.
Vessels in the upper lobes recruit and dilate to accommodate the increased pressure.
3
Identify the finding that corresponds to moderate pressure elevation.
Interstitial edema (Kerley B lines, peribronchial cuffing) appears when pressures reach 18-25 mmHg.
Increased hydrostatic pressure forces fluid into the interstitial spaces but not yet into the alveoli.
4
Determine the imaging finding associated with severe, overwhelming pressure elevation.
Alveolar edema (perihilar opacities) develops when pressures exceed 25 mmHg.
The interstitial capacity is surpassed, leading to fluid extravasation directly into the alveolar airspaces.

Key Concept

Radiographic progression of cardiogenic pulmonary edema
Question 811Question →

A 29-year-old man is brought to the emergency department by paramedics following a high-speed motorcycle collision. On arrival, he is confused and diaphoretic. His temperature is 36.5°C (97.7°F), blood pressure is 82/50 mm Hg, pulse is 128/min, and respiratory rate is 24/min. Physical examination reveals a distended and diffusely tender abdomen with overlying ecchymosis. Breath sounds are equal bilaterally. The pelvis is mechanically stable to manual compression. Intravenous fluid resuscitation is initiated through two large-bore peripheral catheters. Which of the following is the most appropriate initial imaging study for this patient?

Show answer & explanation

Answer: Bedside focused assessment with sonography for trauma (FAST)

Answer

Bedside focused assessment with sonography for trauma (FAST)
The correct answer is a bedside focused assessment with sonography for trauma (FAST). This patient is presenting with hemorrhagic shock (hypotension, tachycardia, altered mental status) following blunt abdominal trauma, as evidenced by a distended, ecchymotic abdomen. According to Advanced Trauma Life Support (ATLS) protocols, the initial diagnostic test of choice for a hemodynamically unstable patient with suspected intra-abdominal hemorrhage is a bedside FAST exam. It is rapid, non-invasive, and highly sensitive for detecting intraperitoneal free fluid (blood). A positive FAST exam in this unstable patient would be an immediate indication for an emergency exploratory laparotomy.

Step-by-Step Solution

1
Identify the patient's hemodynamic status.
The patient is in hemorrhagic shock (hypotension, tachycardia, confusion, diaphoresis).
Hemodynamic status dictates the algorithm for trauma imaging.
2
Localize the most likely source of bleeding based on physical examination.
The distended, tender, and ecchymotic abdomen points to significant intra-abdominal injury.
Directs the provider to image the abdominal cavity first.
3
Select the appropriate imaging modality for an unstable patient with abdominal trauma.
Bedside FAST is chosen.
According to ATLS guidelines, unstable patients cannot leave the resuscitation bay; therefore, rapid bedside imaging with ultrasound is required to confirm intraperitoneal bleeding.

Key Concept

In hemodynamically unstable patients with blunt abdominal trauma, a bedside focused assessment with sonography for trauma (FAST) is the most appropriate initial imaging study to rapidly identify intraperitoneal hemorrhage.
Question 812Question →

A 55-year-old man undergoes an esophagogastroduodenoscopy for a 4-month history of progressive solid-food dysphagia and a 6-kg (13.2-lb) weight loss. He has a 30-pack-year smoking history and consumes several alcoholic beverages daily. Endoscopy reveals an irregular, friable, and ulcerated mass in the middle third of the esophagus. Multiple mucosal biopsies are obtained. The physician suspects squamous cell carcinoma based on the patient's risk factors and tumor location. Which of the following histopathologic biopsy findings would confirm this specific diagnosis? (Select all that apply)

Select all that apply

Show answer & explanation

Answer: Presence of well-formed keratin pearls; Prominent intercellular bridges between malignant cells

Answer

The correct findings are the presence of well-formed keratin pearls and prominent intercellular bridges between malignant cells.
The clinical presentation of an ulcerated mass in the middle third of the esophagus in a patient with a heavy smoking and alcohol history is classic for esophageal squamous cell carcinoma. Establishing this diagnosis definitively requires recognizing the hallmark histopathologic features of squamous differentiation on biopsy. These include the presence of keratin pearls (circular, eosinophilic whorls of keratinized cells) and distinct intercellular bridges (desmosomes connecting adjacent cells). Both of these findings confirm a squamous cell lineage.

Step-by-Step Solution

1
Analyze the clinical vignette to identify the most likely diagnosis based on demographics and location.
The patient's smoking and alcohol history combined with a mid-esophageal mass strongly suggest esophageal squamous cell carcinoma.
Risk factors and anatomic location help differentiate between the two major types of esophageal cancer (squamous cell carcinoma vs. adenocarcinoma) before examining the biopsy.
2
Determine the pathognomonic histopathologic features of squamous cell carcinoma.
Squamous cell carcinoma is histologically characterized by squamous differentiation, which includes keratin pearls and intercellular bridges.
These specific microscopic findings confirm the squamous origin of the malignant cells.
3
Exclude histologic features belonging to alternative esophageal and gastrointestinal malignancies.
Features such as mucin-producing glands and signet ring cells belong to adenocarcinomas, while small round blue cells indicate neuroendocrine tumors.
Accurate biopsy interpretation requires ruling out competing diagnoses in the differential.

Key Concept

Histopathologic identification of esophageal squamous cell carcinoma involves recognizing distinct features of squamous differentiation, primarily keratin pearls and intercellular bridges.
Question 813Question →

An evaluation is requested for a 49-year-old male who reports a 6-month history of voluminous, watery diarrhea and persistent epigastric pain. The patient notes that his symptoms have barely improved despite strict adherence to a high-dose oral omeprazole regimen. His medical history is notable for a duodenal ulcer that perforated and required surgical patch repair one year ago. His vital signs today are within normal limits. Following instructions to discontinue his proton pump inhibitor for seven days, the patient underwent an upper gastrointestinal endoscopy, which demonstrated unusually thickened gastric folds and the presence of two distinct ulcers in the postbulbar duodenum. Subsequent laboratory analysis reveals a fasting serum gastrin concentration of 580 pg/mL580 \text{ pg/mL} (normal: <100 pg/mL< 100 \text{ pg/mL}) and a basal gastric pH of 1.41.4. Which of the following is the most appropriate next step in the diagnostic workup?

Show answer & explanation

Answer: Secretin stimulation test

Answer

The correct next step is the secretin stimulation test.
The patient's clinical presentation is highly suspicious for Zollinger-Ellison syndrome (ZES), caused by a gastrin-secreting neuroendocrine tumor (gastrinoma). The diagnostic workup for ZES begins with measuring fasting serum gastrin (FSG) and basal gastric pH. A gastric pH <2.0< 2.0 indicates that the hypergastrinemia is primary. If the FSG is >1000 pg/mL> 1000 \text{ pg/mL} with a pH <2.0< 2.0, the diagnosis of ZES is confirmed. However, if the FSG is elevated but <1000 pg/mL< 1000 \text{ pg/mL} (as in this patient with 580 pg/mL580 \text{ pg/mL}), the results are considered equivocal. In such cases, a secretin stimulation test is required. Secretin normally inhibits gastrin release from normal gastric G cells but paradoxically stimulates gastrin release from gastrinoma cells. An increase in serum gastrin of >120 pg/mL> 120 \text{ pg/mL} above the basal level confirms the diagnosis of ZES.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and endoscopic findings.
The patient has refractory peptic ulcer disease, postbulbar ulcers, and chronic diarrhea, which are classic hallmark signs of Zollinger-Ellison syndrome (ZES).
Identifying the clinical syndrome guides the initial diagnostic hypothesis and determines the appropriateness of the preliminary tests.
2
Evaluate the preliminary laboratory results in the context of the medication history.
The fasting serum gastrin is elevated at 580 pg/mL580 \text{ pg/mL}, and the gastric pH is highly acidic at 1.41.4, obtained after appropriately holding proton pump inhibitors.
A low gastric pH confirms that the hypergastrinemia is primary (gastrin-driven) rather than secondary to achlorhydria, ruling out conditions like atrophic gastritis.
3
Determine the appropriate diagnostic sequence based on the specific gastrin level.
Because the gastrin level falls in the equivocal range (between 110110 and 1000 pg/mL1000 \text{ pg/mL}), a secretin stimulation test is required to definitively confirm the diagnosis before proceeding to any anatomic imaging.
Following algorithmic guidelines prevents premature and unnecessary invasive testing or advanced imaging.

Key Concept

In the workup of suspected Zollinger-Ellison syndrome, a fasting serum gastrin level between 110110 and 1000 pg/mL1000 \text{ pg/mL} with an acidic gastric pH (<2.0< 2.0) is equivocal and requires a secretin stimulation test for definitive biochemical confirmation prior to anatomic tumor localization.
Estimated Time:1m 30s
Question 814Question →

A 60-year-old man with a 30-pack-year smoking history undergoes a routine chest radiograph prior to an elective inguinal hernia repair. The radiograph reveals an incidental 12-mm solid nodule in the right upper lobe. He has no respiratory symptoms, fever, or weight loss. Arrange the following diagnostic and imaging steps in the most appropriate standard chronological sequence for evaluating this incidental solitary pulmonary nodule, assuming each non-invasive step continues to suggest an intermediate-to-high risk of malignancy.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is to first review historical imaging, followed by a dedicated non-contrast chest CT, then a PET scan, and finally a CT-guided percutaneous biopsy.
The evaluation of an incidental pulmonary nodule follows a strict algorithm to minimize unnecessary invasive testing. The crucial first step is comparing the finding with prior imaging to assess for stability over at least two years. If prior imaging is unavailable or shows growth, a dedicated non-contrast chest CT is required to define the anatomical features of the nodule. For intermediate-risk solid nodules >8 mm, a PET scan is the next step to assess metabolic activity and evaluate for occult mediastinal metastasis. Only after these non-invasive imaging modalities suggest a high likelihood of malignancy and appropriately stage the patient should a tissue diagnosis via CT-guided biopsy be pursued.

Step-by-Step Solution

1
Obtain and review prior chest imaging.
Determines if the nodule is new, growing, or stable.
Demonstrating stability over 24 months reliably indicates benignity, thereby avoiding unnecessary radiation, invasive procedures, and healthcare costs.
2
Perform a thin-section non-contrast chest CT.
Characterizes the nodule's morphology, exact size, and attenuation.
CT provides detailed anatomical resolution essential for risk stratification (e.g., assessing for spiculation or benign calcification patterns) and is the gold standard following an abnormal radiograph.
3
Obtain a PET scan.
Evaluates the metabolic activity of the nodule and screens for regional metastasis.
For solid nodules >8 mm with intermediate malignancy probability, PET scanning helps determine the yield of a biopsy and non-invasively stages the mediastinal lymph nodes.
4
Perform a CT-guided percutaneous core needle biopsy.
Provides tissue for histopathological diagnosis.
Once imaging confirms a high suspicion for malignancy and assesses spread, definitive tissue sampling is required before initiating surgical or oncological treatment.

Key Concept

Step-wise radiologic evaluation of a solitary pulmonary nodule based on size and risk stratification.
Question 815Question →

A 62-year-old woman is brought to the emergency department by her daughter due to profound generalized weakness and near-syncope that started earlier this morning. The patient has a history of type 2 diabetes mellitus, hypertension, and end-stage renal disease for which she receives hemodialysis three days a week. She missed her last two dialysis sessions due to transportation issues. On physical examination, she appears lethargic and pale. Vital signs are temperature 36.8°C (98.2°F), blood pressure 82/48 mm Hg, pulse 38/min, and respiratory rate 22/min. Oxygen saturation is 97% on ambient air. Cardiac auscultation reveals severe bradycardia without murmurs. A stat 12-lead electrocardiogram is obtained immediately upon arrival, demonstrating absent P waves and markedly widened QRS complexes that merge seamlessly with the T waves. Which of the following is the most appropriate immediate next step in the management of this patient?

Show answer & explanation

Answer: Administer intravenous calcium gluconate

Answer

Administer intravenous calcium gluconate
Intravenous calcium gluconate is the most appropriate immediate next step for a patient presenting with hemodynamic instability and electrocardiographic evidence of severe hyperkalemia (sine wave pattern). Calcium directly antagonizes the membrane-depolarizing effects of potassium, stabilizing the cardiac conduction system and preventing impending ventricular fibrillation or asystole. This must be given immediately before shifting potassium intracellularly or removing it from the body.

Step-by-Step Solution

1
Analyze the clinical presentation and history.
The patient is a dialysis-dependent individual who missed recent sessions, presenting with hemodynamic instability (hypotension, severe bradycardia) and generalized weakness.
Identifying the patient's end-stage renal disease and missed dialysis raises high clinical suspicion for life-threatening metabolic derangements, most notably hyperkalemia.
2
Interpret the immediate diagnostic findings.
The 12-lead electrocardiogram demonstrates absent P waves and widened QRS complexes merging into T waves (a 'sine wave' pattern).
These specific ECG changes in the context of missed dialysis are virtually pathognomonic for severe, advanced hyperkalemia with impending cardiac arrest.
3
Determine the priority of interventions based on acuity.
The patient is hemodynamically unstable; therefore, immediate cardiac membrane stabilization takes precedence over definitive potassium-lowering therapies or diagnostic confirmation.
Initial stabilization and triage protocols dictate that reversing the most immediate life-threatening physiological threat (ventricular fibrillation/asystole) is the absolute first step.
4
Select the appropriate pharmacologic intervention.
Intravenous calcium gluconate (or calcium chloride) is selected as the next best step.
Calcium acts rapidly (within minutes) to restore the resting membrane potential of cardiac myocytes, providing crucial time to initiate therapies that actually lower serum potassium.

Key Concept

In patients presenting with severe hyperkalemia characterized by electrocardiographic changes (e.g., widened QRS, sine wave pattern) or hemodynamic instability, the immediate first step in stabilization is the administration of intravenous calcium to stabilize the cardiac myocyte membrane and prevent fatal arrhythmias.
Question 816Question →

An independent 6969-year-old gentleman is brought to the emergency department by emergency medical services after his wife found him unable to walk. He reports severe, unrelenting pain between his shoulder blades that started 33 days ago. Over the past 88 hours, he developed profound weakness in both legs and an inability to void.

His medical history is significant for type 2 diabetes mellitus, hemodialysis-dependent end-stage renal disease, and sick sinus syndrome. He had a permanent dual-chamber pacemaker implanted 1515 years ago; device interrogation reveals it is a legacy, non-MRI-conditional model.

Vital signs include a temperature of 38.9∘C38.9^\circ\text{C} (102.0∘F102.0^\circ\text{F}), blood pressure of 112/68 mm Hg112/68\text{ mm Hg}, heart rate of 104/min104/\text{min}, and respiratory rate of 16/min16/\text{min}. Physical examination demonstrates marked point tenderness over the T9 and T10 spinous processes. Neurologic evaluation reveals 2/52/5 strength in the proximal and distal lower extremities bilaterally. There is absent sensation to pinprick and temperature below the level of the umbilicus. Patellar and Achilles reflexes are 3+3+ bilaterally with sustained clonus, and a Babinski sign is present bilaterally. Post-void residual volume by bladder scan is 650 mL650\text{ mL}.

Laboratory studies show a leukocyte count of 19,200/μL19,200/\mu\text{L} and an erythrocyte sedimentation rate of 115 mm/h115\text{ mm/h}. The physician suspects a spinal epidural abscess with acute cord compression.

Which of the following is the most appropriate next step in imaging?

Show answer & explanation

Answer: Computed tomography (CT) myelography of the thoracic spine

Answer

Computed tomography (CT) myelography of the thoracic spine
The correct answer is Computed tomography (CT) myelography of the thoracic spine. This patient presents with the classic triad of a spinal epidural abscess (SEA): fever, focal back pain, and neurologic deficits. The acute onset of paraparesis, a T10 sensory level (indicated by anesthesia below the umbilicus), and urinary retention point to an emergent thoracic spinal cord compression. The gold standard for evaluating SEA is an MRI of the spine with intravenous gadolinium. However, this patient has a legacy, non-MRI-conditional pacemaker, which is an absolute contraindication to MRI due to the risk of device movement, thermal injury, and fatal arrhythmias. In patients who cannot undergo MRI, CT myelography is the diagnostic imaging modality of choice. It involves the injection of radiopaque contrast directly into the subarachnoid space, followed by a CT scan. This technique provides excellent delineation of the thecal sac and reliably identifies extrinsic compression from an epidural abscess, allowing for emergent surgical planning.

Step-by-Step Solution

1
Identify the clinical syndrome
The patient has the classic triad of a spinal epidural abscess (SEA): fever, localized back pain, and progressive neurologic deficits (paraparesis, sensory level at T10, urinary retention).
Recognizing acute spinal cord compression is critical to guide emergent diagnostic imaging and prevent permanent paralysis.
2
Determine the gold standard imaging modality
MRI of the spine with intravenous gadolinium is the preferred and most sensitive study for this condition.
MRI provides superior soft-tissue contrast to visualize the epidural fluid collection and assess the degree of thecal sac compression.
3
Assess for patient-specific contraindications
The patient has a 15-year-old legacy pacemaker that is non-MRI-conditional.
Subjecting this patient to an MRI magnetic field could cause catastrophic device movement, heating, or lethal arrhythmias, making MRI strictly contraindicated.
4
Select the best alternative imaging modality
CT myelography is selected as the next step in imaging.
When MRI is unavailable or contraindicated, CT myelography (using intrathecal contrast) is the most accurate alternative to visualize the subarachnoid space and diagnose extrinsic cord compression.

Key Concept

When magnetic resonance imaging (MRI) is strictly contraindicated (e.g., due to a legacy pacemaker), computed tomography (CT) myelography is the alternative imaging modality of choice to evaluate for a spinal epidural abscess and acute spinal cord compression.
Estimated Time:1m 30s
Question 817Question →

A 37-year-old man is evaluated for a palpable, non-tender nodule in the right anterior neck, discovered incidentally during a routine physical examination. He reports no dysphagia, hoarseness, or systemic symptoms. His serum thyroid-stimulating hormone (TSH) level is 1.8μU/mL1.8 \mu\text{U/mL} (normal: 0.4−4.0μU/mL0.4-4.0 \mu\text{U/mL}). A neck ultrasound reveals a 1.8 cm1.8\text{ cm} solid, hypoechoic nodule in the right thyroid lobe with irregular margins and punctate microcalcifications. A fine-needle aspiration (FNA) biopsy of the nodule is performed to establish a definitive diagnosis. Which of the following specific cytologic features, if identified on the aspiration specimen, would definitively establish a diagnosis of papillary thyroid carcinoma in this patient? (Select all that apply)

Select all that apply

Show answer & explanation

Answer: Intranuclear cytoplasmic inclusions (pseudoinclusions); Longitudinal nuclear grooves (coffee bean nuclei)

Answer

The correct diagnostic features are intranuclear cytoplasmic inclusions (pseudoinclusions) and longitudinal nuclear grooves.
Papillary thyroid carcinoma (PTC) is uniquely characterized by defining nuclear atypia that can be definitively identified on cytologic smears from a fine-needle aspiration. The pathognomonic findings required to confirm this diagnosis include enlarged, overlapping nuclei with cleared or empty-appearing chromatin (optically clear or 'Orphan Annie eye' nuclei), longitudinal nuclear grooves that give the nuclei a 'coffee bean' appearance, and distinct intranuclear cytoplasmic pseudoinclusions (invaginations of the cytoplasm into the nucleus). Identifying these specific features firmly establishes the diagnosis and guides subsequent surgical management.

Step-by-Step Solution

1
Analyze the clinical and sonographic presentation.
The patient is a euthyroid man with a thyroid nodule showing highly suspicious ultrasound features for malignancy (solid, hypoechoic, irregular margins, microcalcifications).
Identifying the pre-test probability guides the interpretation of the fine-needle aspiration (FNA) results.
2
Determine the diagnostic capabilities of FNA for this pathology.
FNA is highly accurate for diagnosing papillary thyroid carcinoma (PTC) based purely on distinctive nuclear architecture.
Unlike follicular carcinoma, which requires histologic evaluation of the tumor capsule, PTC can be definitively diagnosed on cytology alone.
3
Identify the pathognomonic cytologic features of papillary thyroid carcinoma.
The defining features are nuclear: enlarged, optically clear nuclei ('Orphan Annie eyes'), intranuclear pseudoinclusions, and longitudinal nuclear grooves.
Selecting the options that match these specific histologic criteria confirms the diagnosis of PTC.

Key Concept

Fine-needle aspiration (FNA) cytology can definitively diagnose papillary thyroid carcinoma through the identification of characteristic nuclear atypia, specifically intranuclear pseudoinclusions, longitudinal nuclear grooves, and optically clear chromatin.
Question 818Question →

A 62-year-old man is brought to the emergency department by ambulance due to the sudden onset of severe, "tearing" chest pain that radiates to his back, between the shoulder blades. The pain began 3030 minutes ago while he was resting. He has a medical history of poorly controlled hypertension, hyperlipidemia, and a 4040-pack-year smoking history. On presentation, he appears in acute distress, anxious, and diaphoretic. Vital signs are temperature 37.0∘C37.0^\circ\text{C} (98.6∘F98.6^\circ\text{F}), blood pressure 215/115215/115 mm Hg in the right arm and 205/110205/110 mm Hg in the left arm, heart rate 118118/min, and respiratory rate 2222/min. Oxygen saturation is 97%97\% on room air. Cardiovascular examination reveals a regular tachycardia and a new, faint decrescendo diastolic murmur heard best at the right upper sternal border. The lungs are clear to auscultation bilaterally. An electrocardiogram shows sinus tachycardia and voltage criteria for left ventricular hypertrophy, but no acute ischemic changes. Which of the following is the most appropriate immediate next step in management?

Show answer & explanation

Answer: Administer intravenous esmolol

Answer

Administer intravenous esmolol
The clinical presentation of sudden-onset, severe, tearing chest pain radiating to the back in a highly hypertensive patient is classic for an acute aortic dissection. The new decrescendo diastolic murmur indicates aortic regurgitation, suggesting proximal extension of the dissection flap (Type A). The immediate priority in patient management (initial stabilization) is 'anti-impulse' therapy to rapidly lower the heart rate (target ≤60\leq 60/min) and systolic blood pressure (target 100−120100-120 mm Hg). This reduces the left ventricular ejection force and aortic wall shear stress (dP/dtdP/dt), minimizing the risk of dissection propagation and rupture. Intravenous beta-blockers (e.g., esmolol, labetalol, or propranolol) are the drugs of choice and must be administered as the absolute first step in management, even before definitive diagnostic imaging is obtained.

Step-by-Step Solution

1
Analyze the clinical presentation and physical exam findings.
The patient's sudden-onset tearing back pain, severe hypertension, and new murmur of aortic regurgitation strongly suggest an acute aortic dissection.
Establishing a high-confidence working diagnosis directs the immediate triage and stabilization pathway, separating it from acute coronary syndrome protocols.
2
Determine the most critical stabilization priority.
The immediate goal is to rapidly reduce aortic wall shear stress (dP/dt) to prevent dissection propagation and catastrophic rupture.
Hemodynamic instability and continued high mechanical stress on the aortic wall are the primary causes of early mortality in acute aortic dissection.
3
Select the appropriate initial pharmacologic intervention.
Intravenous beta-blockers (such as esmolol or labetalol) are the first-line agents to lower heart rate to ≤60\leq 60/min and systolic blood pressure to 100−120100-120 mm Hg.
Beta-blockers must be administered as the absolute first step in management, before definitive imaging and before any vasodilators are given.

Key Concept

In suspected acute aortic dissection, immediate initial stabilization requires anti-impulse therapy with intravenous beta-blockers to reduce heart rate and blood pressure before definitive diagnostic imaging or administration of vasodilators.
Question 819Question →

A 50-year-old man undergoes an upper gastrointestinal endoscopy to evaluate a 5-year history of chronic heartburn. During the procedure, the gastroenterologist notes an area of abnormal-appearing mucosa in the distal esophagus and takes a biopsy. The resulting pathology report states: 'Replacement of the normal stratified squamous epithelium by columnar epithelium with interspersed goblet cells. No dysplasia or invasive cells are identified.' Based on this biopsy interpretation, what is the most likely diagnosis?

Show answer & explanation

Answer: Barrett esophagus

Answer

Barrett esophagus
The correct answer is Barrett esophagus. The biopsy explicitly describes the replacement of native stratified squamous epithelium with columnar epithelium containing goblet cells in the distal esophagus. This process is known as intestinal metaplasia and is the definitive pathologic requirement for diagnosing Barrett esophagus, which typically develops as a complication of chronic gastroesophageal reflux disease.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has a long history of chronic heartburn, which is a major risk factor for complications of gastroesophageal reflux disease (GERD).
Establishing the clinical context helps narrow the differential diagnosis for esophageal pathology.
2
Interpret the biopsy findings from the pathology report.
The report describes columnar epithelium with goblet cells replacing the normal stratified squamous epithelium.
Identifying the specific histologic changes is required to establish the correct definitive diagnosis.
3
Correlate the histology with the specific condition.
Intestinal metaplasia (goblet cells in columnar epithelium) in the distal esophagus is diagnostic of Barrett esophagus.
This histologic hallmark distinguishes Barrett esophagus from simple reflux esophagitis or malignancies.

Key Concept

Intestinal metaplasia, defined by the presence of goblet cells replacing the normal squamous epithelium in the distal esophagus, is the diagnostic histologic feature of Barrett esophagus.
Estimated Time:45s
Question 820Question →

A central neuropathology laboratory is reviewing surgical biopsy specimens from four different patients who presented with progressive neurologic deficits and primary intracranial masses on magnetic resonance imaging (MRI). Match each distinct histopathologic, immunohistochemical, and molecular profile with the most likely definitive pathologic diagnosis.

Click a left item, then click its matching right item

Items

Highly cellular proliferation of small, round, hyperchromatic cells forming Homer Wright rosettes; cytogenetic analysis reveals the presence of isochromosome 17q.
Whorls of spindled cells accompanied by abundant calcified psammoma bodies; immunohistochemistry demonstrates strong, diffuse positivity for somatostatin receptor 2A (SSTR2a) and epithelial membrane antigen (EMA).
GFAP-positive neoplasm demonstrating prominent perivascular pseudorosettes and true rosettes; tumor cells exhibit characteristic dot-like cytoplasmic EMA positivity.
Infiltrating astrocytic proliferation featuring pseudopalisading necrosis and microvascular proliferation; molecular testing confirms an IDH-wildtype profile and EGFR amplification.

Matches

Show answer & explanation

Answer

1 matches with Medulloblastoma; 2 matches with Meningioma; 3 matches with Ependymoma; 4 matches with Glioblastoma.
Each tumor profile contains pathognomonic features that secure the diagnosis according to WHO CNS tumor classification criteria. Medulloblastomas feature small round blue cells with Homer Wright rosettes and frequently isochromosome 17q. Meningiomas present with meningothelial whorls, psammoma bodies, and SSTR2a positivity. Ependymomas demonstrate perivascular pseudorosettes with unique dot-like EMA positivity. Glioblastomas are defined by pseudopalisading necrosis, microvascular proliferation, and an IDH-wildtype profile.

Step-by-Step Solution

1
Analyze the first biopsy profile noting the small round blue cells, Homer Wright rosettes, and isochromosome 17q.
Identify the profile as Medulloblastoma.
These are the classic morphologic and genetic hallmarks of this pediatric embryonal tumor.
2
Evaluate the second profile featuring meningothelial whorls, psammoma bodies, and SSTR2a positivity.
Identify the profile as Meningioma.
SSTR2a and EMA positivity paired with whorled architecture definitively diagnoses a meningioma.
3
Assess the third profile showing GFAP-positivity, perivascular pseudorosettes, and dot-like EMA positivity.
Identify the profile as Ependymoma.
While both ependymomas and some other gliomas express GFAP, the true rosettes and dot-like EMA positivity are highly specific for ependymoma.
4
Review the fourth profile characterized by pseudopalisading necrosis, microvascular proliferation, and IDH-wildtype status.
Identify the profile as Glioblastoma.
The combination of necrosis, microvascular proliferation, and IDH-wildtype status confirms a high-grade astrocytoma (glioblastoma).

Key Concept

Definitive diagnosis of central nervous system tumors requires integrating microscopic architectural patterns (e.g., specific rosette types, whorls, necrosis) with targeted immunohistochemical markers (e.g., EMA, GFAP, SSTR2a) and molecular/cytogenetic profiles (e.g., IDH status, isochromosome 17q).
Estimated Time:1m 30s
PreviousPage 41 / 237Next
All practice questions — USMLE Step 3 | Examkin