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Difficulty: HardBreast and Endocrine Surgery

A 45-year-old woman is referred to the surgical clinic for evaluation of a neck mass she noticed while applying lotion. She reports a 4-kg (8.8-lb) weight loss over the past 3 months despite an increased appetite, as well as occasional palpitations. She has no personal or family history of head and neck irradiation or endocrine malignancies. Vital signs are within normal limits except for a heart rate of 102/min. Physical examination reveals a 3-cm, firm, non-tender, mobile nodule in the right thyroid lobe. Laboratory studies show:

Thyroid-stimulating hormone (TSH): 0.05 µU/mL (normal: 0.4–4.0 µU/mL)
Free thyroxine (T4): 2.4 ng/dL (normal: 0.8–1.8 ng/dL)

A dedicated neck ultrasound demonstrates a 3.2-cm solid, markedly hypoechoic nodule in the right lobe with irregular margins and internal microcalcifications. No abnormal cervical lymph nodes are identified. Which of the following is the most appropriate next step in management?

  1. Radionuclide thyroid imagingAnswer
  2. B
    Fine-needle aspiration biopsy of the nodule
  3. C
    Right thyroid lobectomy
  4. D
    Initiation of levothyroxine therapy
  5. E
    Measurement of serum calcitonin

Answer

Radionuclide thyroid imaging
The correct answer is radionuclide thyroid imaging. The initial evaluation of any thyroid nodule greater than 1 cm begins with a serum TSH level and a targeted thyroid ultrasound. When the TSH is subnormal (indicating overt or subclinical hyperthyroidism), the most appropriate next step is a radionuclide thyroid scan (using iodine-123 or technetium-99m) to determine the functional status of the nodule. If the scan demonstrates a hyperfunctioning ('hot') nodule, the risk of malignancy is extremely low, and a fine-needle aspiration (FNA) biopsy is contraindicated, regardless of how suspicious the ultrasound features appear. If the nodule is nonfunctioning ('cold'), an FNA biopsy is then indicated based on the ultrasound criteria. This question tests the physician's ability to rigidly adhere to the diagnostic algorithm despite alarming sonographic features.

Step-by-Step Solution

1
Analyze the patient's clinical and laboratory presentation.
The patient has a 3-cm palpable thyroid nodule with symptomatic thyrotoxicosis, confirmed by a suppressed TSH and elevated Free T4.
Establishing the biochemical thyroid status is the mandatory first step in evaluating any thyroid nodule >1 cm.
2
Evaluate the ultrasound findings.
The ultrasound shows high-risk features for malignancy (solid, hypoechoic, irregular margins, microcalcifications).
Ultrasound determines the size and suspicious characteristics of the nodule.
3
Apply the standard diagnostic algorithm for a thyroid nodule based on the TSH level.
Because the TSH is subnormal, the algorithm requires a radionuclide thyroid scan as the immediate next step, overriding the ultrasound features.
A radionuclide scan differentiates a hyperfunctioning ('hot') nodule from a nonfunctioning ('cold') nodule. Hyperfunctioning nodules have an extremely low risk of malignancy (<1%) and do not require fine-needle aspiration, whereas cold nodules with suspicious features must be biopsied.

Key Concept

Diagnostic workup of a thyroid nodule with a suppressed TSH requires radionuclide imaging prior to any consideration of fine-needle aspiration.
Estimated Time:1m 30s
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Topics

Breast and Endocrine Surgery

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