A 24-year-old woman is evaluated for a lump in her neck. She discovered the lump a week ago while showering. The patient feels well and has no associated pain, fever, night sweats, or weight changes. Her medical history is unremarkable, although she has had irregular menses for a year since insertion of an intrauterine device. The patient does not use tobacco, alcohol, or illicit drugs. Her mother died during surgery for thyroid cancer. Blood pressure is 133/80 mm Hg and pulse is 78/min. On examination, there is a palpable 2-cm nodule in the right thyroid lobe. The remainder of the examination, including chest, abdomen, extremities, and skin, is normal. Serum TSH and calcium levels are normal and calcitonin is elevated. Ultrasound-guided aspiration biopsy reveals malignant cells. Which of the following tests is the best next step in evaluation of this patient?

Question

A 24-year-old woman is evaluated for a lump in her neck.  She discovered the lump a week ago while showering.  The patient feels well and has no associated pain, fever, night sweats, or weight changes.  Her medical history is unremarkable, although she has had irregular menses for a year since insertion of an intrauterine device.  The patient does not use tobacco, alcohol, or illicit drugs.  Her mother died during surgery for thyroid cancer.  Blood pressure is 133/80 mm Hg and pulse is 78/min.  On examination, there is a palpable 2-cm nodule in the right thyroid lobe.  The remainder of the examination, including chest, abdomen, extremities, and skin, is normal.  Serum TSH and calcium levels are normal and calcitonin is elevated.  Ultrasound-guided aspiration biopsy reveals malignant cells.  Which of the following tests is the best next step in evaluation of this patient?

Quizplus · Accepted Answer

11ec25c8_d12f_7d1f_bc81_f3e198ef1989_MD0003_00 This patient with a malignant thyroid mass, elevated serum calcitonin level, and family history of thyroid malignancy likely has an inherited form of medullary thyroid cancer (MTC). MTC is a calcitonin-producing tumor arising from neuroendocrine parafollicular C cells of the thyroid gland. Although most MTC is sporadic, approximately one third of MTC is inherited as a component of multiple endocrine neoplasia (MEN) types 2A and 2B. MEN 2A and 2B (usually due to RET proto-oncogene mutations) are also associated with pheochromocytoma, which can be asymptomatic at the time of diagnosis but cause life-threatening hypertensive crisis during surgical procedures (eg, thyroidectomy). In light of this risk, most patients with MTC should undergo RET mutation testing and screening for pheochromocytoma with a plasma fractionated metanephrine assay. If found, pheochromocytoma should be resected prior to thyroidectomy. (Choices A, B, and C) The aldosterone-renin activity ratio can help evaluate hyperaldosteronism (eg, hypertension, hypernatremia, hypokalemia). The low-dose dexamethasone suppression test and the salivary cortisol test are helpful in screening for Cushing syndrome (eg, obesity, facial plethora, easy bruising). This patient has no manifestations of these conditions. In addition, adrenocortical tumors are uncommon in MEN syndromes, with biochemical testing recommended only in patients with manifestations of excessive hormonal production. (Choices E and F) Serum prolactin and insulin-like growth factor-1 are screening tests for prolactin and growth hormone-secreting pituitary tumors. Pituitary tumors occur in MEN1 but are not a feature of MEN2. Educational objective: Medullary thyroid cancer (MTC) is a calcitonin-producing tumor of the thyroid parafollicular C cells. It often occurs as a component of multiple endocrine neoplasia types 2A and 2B, which are also associated with pheochromocytoma. Patients with MTC should be screened for pheochromocytoma prior to thyroidectomy with a plasma fractionated metanephrine assay. References: Genetics, diagnosis, and management of medullary thyroid carcinoma and pheochromocytoma/paraganglioma. (http://www.ncbi.nlm.nih.gov/pubmed/24449662)

A 24-Year-Old Woman Is Evaluated for a Lump in Her