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Difficulty: EasyDiagnostic Workup and Test Sequencing

A 35-year-old woman comes to the clinic for evaluation of a painless lump in her neck that she noticed two weeks ago while applying moisturizer. She reports no changes in weight, bowel habits, energy levels, or temperature tolerance. She has no significant past medical history and takes no medications. Vital signs are within normal limits. Physical examination reveals a 1.5-cm, firm, mobile, non-tender nodule in the right lobe of the thyroid gland. No cervical lymphadenopathy is appreciated. Laboratory testing shows a serum thyroid-stimulating hormone (TSH) level of 2.8 µU/mL (reference range: 0.5–5.0 µU/mL). Which of the following is the most appropriate next step in the diagnostic workup?

  1. Ultrasound of the neckAnswer
  2. B
    Fine-needle aspiration biopsy of the nodule
  3. C
    Radioactive iodine uptake scan
  4. D
    Computed tomography scan of the neck with intravenous contrast
  5. E
    Measurement of serum thyroglobulin level

Answer

Ultrasound of the neck is the most appropriate next step to evaluate the sonographic features of the thyroid nodule.
The correct answer is ultrasound of the neck. The standard sequence for evaluating a newly discovered thyroid nodule begins with a serum TSH level and a neck ultrasound. When the TSH is normal or elevated, a neck ultrasound is definitively the next step to assess the nodule's size and sonographic features (such as solid composition, hypoechogenicity, irregular margins, or microcalcifications). This risk-stratifies the nodule and determines whether a fine-needle aspiration (FNA) biopsy is required.

Step-by-Step Solution

1
Identify the primary clinical problem.
The patient has a new, palpable, 1.5-cm thyroid nodule.
Establishing the chief complaint dictates the diagnostic algorithm.
2
Evaluate the initial laboratory findings.
The TSH level is 2.8 µU/mL, which is within normal limits.
TSH levels determine the functional status of the nodule and dictate whether anatomic (ultrasound) or functional (radionuclide scan) imaging is prioritized.
3
Select the guideline-indicated next step based on the TSH result.
Because the TSH is normal (or elevated), a neck ultrasound is indicated to characterize the nodule.
Ultrasound evaluates features such as margins, echogenicity, and microcalcifications, which stratify the risk of malignancy and determine if a biopsy is ultimately needed.

Key Concept

The initial evaluation of a thyroid nodule requires measuring a TSH level; if the TSH is normal or elevated, a neck ultrasound is the next appropriate step.
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Diagnostic Workup and Test Sequencing

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