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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 42-year-old woman presents to the outpatient clinic for evaluation of a neck lump she noticed two weeks ago while applying lotion. She denies dysphagia, dysphonia, weight changes, palpitations, tremors, or cold intolerance. Her medical history is unremarkable, and she takes no medications. She has no personal or family history of head or neck radiation or thyroid cancer. Vital signs include a blood pressure of 118/76 mmHg, pulse of 72/min, and temperature of 37.0°C (98.6°F). Physical examination reveals a palpable, 2.5-cm, firm, mobile, non-tender nodule in the right lobe of the thyroid gland. The remainder of the thyroid gland is not enlarged, and there is no cervical lymphadenopathy. Which of the following tests should be ordered as the INITIAL steps in evaluating this patient's nodule? (Select the two most appropriate tests)

  1. Measurement of serum thyroid-stimulating hormoneAnswer
  2. Thyroid ultrasonographyAnswer
  3. C
    Fine-needle aspiration biopsy of the nodule
  4. D
    Radionuclide thyroid scan (iodine-123)
  5. E
    Computed tomography scan of the neck with intravenous contrast
  6. F
    Measurement of serum thyroglobulin

Answer

The correct initial steps are the measurement of serum thyroid-stimulating hormone (TSH) and thyroid ultrasonography.
The initial evaluation of any newly discovered thyroid nodule requires two concurrent steps: evaluating the functional status of the thyroid gland and assessing the anatomical characteristics of the nodule. Measurement of serum thyroid-stimulating hormone (TSH) is the most sensitive test for determining thyroid function. Thyroid ultrasonography is the imaging modality of choice to confirm the presence of a nodule, measure its exact dimensions, evaluate for suspicious sonographic features (e.g., solid composition, hypoechogenicity, irregular margins, microcalcifications), and check for abnormal cervical lymph nodes. Together, these two tests dictate the subsequent algorithm, specifically determining whether the patient requires a radionuclide scan or an ultrasound-guided fine-needle aspiration biopsy.

Step-by-Step Solution

1
Identify the primary clinical problem
The patient presents with an asymptomatic, palpable thyroid nodule with no clinical signs of hyperthyroidism or hypothyroidism.
Establishing the clinical baseline directs whether emergency stabilization or routine diagnostic workup is required.
2
Determine the first-line biochemical evaluation
Select serum TSH measurement.
TSH determines the functional status of the nodule. A low TSH indicates a hyperfunctioning nodule (requiring a radionuclide scan), whereas a normal or high TSH requires risk stratification for malignancy.
3
Determine the first-line anatomical evaluation
Select thyroid ultrasonography.
Ultrasound provides the necessary anatomical details (size, composition, margins, echogenicity, microcalcifications) to stratify the risk of malignancy and determine if a biopsy is indicated.

Key Concept

The initial concurrent workup of a newly discovered thyroid nodule consists of both a biochemical assessment (serum TSH) and an anatomical assessment (thyroid ultrasonography).
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Diagnostic Workup and Test Sequencing

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