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Difficulty: MediumBreast and Endocrine Surgery

A 42-year-old woman is evaluated in the surgical oncology clinic after a 2.5-cm left thyroid nodule was discovered during a routine physical examination. Fine-needle aspiration of the nodule reveals malignant cells with amorphous, eosinophilic extracellular material that stains positive with Congo red. She is scheduled for a total thyroidectomy and central neck lymph node dissection. The patient has no history of neck radiation and no family history of endocrine disorders. Her blood pressure is 125/80 mm Hg and pulse is 76/min. Which of the following is the most appropriate next step in the preoperative evaluation of this patient?

  1. A
    Measurement of serum thyroglobulin levels
  2. B
    Administration of radioactive iodine (I-131)
  3. Measurement of plasma fractionated metanephrinesAnswer
  4. D
    Sestamibi parathyroid scintigraphy
  5. E
    Initiation of thyroid-stimulating hormone suppression therapy

Answer

Measurement of plasma fractionated metanephrines
The patient's fine-needle aspiration demonstrates amyloid (Congo red-positive material), which is pathognomonic for medullary thyroid cancer (MTC). MTC arises from the parafollicular C cells of the thyroid and can occur sporadically or as a component of Multiple Endocrine Neoplasia (MEN) type 2A or 2B. Because MEN2 syndromes are associated with pheochromocytoma in up to 50% of cases, all patients with a new diagnosis of MTC must undergo biochemical screening for a pheochromocytoma (e.g., measurement of plasma fractionated metanephrines) prior to any surgical procedure. If a pheochromocytoma is present, it must be removed first after appropriate alpha-adrenergic blockade to prevent a potentially fatal intraoperative hypertensive crisis during the thyroidectomy.

Step-by-Step Solution

1
Identify the primary diagnosis from the fine-needle aspiration findings.
The presence of malignant cells with Congo red-positive amorphous eosinophilic material indicates amyloid, which is diagnostic of medullary thyroid cancer (MTC).
Correctly identifying the tumor type is essential for determining the appropriate preoperative workup.
2
Recognize the genetic syndromic associations of the diagnosed cancer.
MTC is heavily associated with Multiple Endocrine Neoplasia type 2 (MEN2A and MEN2B).
Up to 25% of MTC cases are familial and part of a MEN2 syndrome.
3
Determine the necessary safety evaluations prior to surgical intervention.
Patients with suspected MEN2 must be evaluated for a coexisting pheochromocytoma using plasma fractionated metanephrines or 24-hour urine metanephrines.
Operating on a patient with an unrecognized pheochromocytoma can precipitate a lethal intraoperative hypertensive crisis. This must be ruled out before any surgery, including thyroidectomy, is performed.

Key Concept

All patients with medullary thyroid cancer must be screened for a coexisting pheochromocytoma (via plasma fractionated metanephrines) prior to thyroidectomy to prevent an intraoperative hypertensive crisis.
Estimated Time:1m 15s
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Topics

Breast and Endocrine Surgery

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