The next most appropriate step in the management of this patient with medullary thyroid cancer (MTC) and multiple endocrine neoplasia type 2A (MEN2A) is to evaluate for the presence of a pheochromocytoma by measurement of fractionated plasma metanephrines. All patients with a cytologic diagnosis of MTC should undergo testing of the tumor for genetic abnormalities as the initial step in their evaluation as 25% of patients with MTC will have the inherited form. Identification of a RET mutation in this patient means that the he has MEN2A, an inherited syndrome associated with hyperparathyroidism and pheochromocytoma. Failure to identify and treat a pheochromocytoma prior to surgery can result in an intraoperative hypertensive crisis and, potentially, death.

While it is important to assess the risk of metastatic disease in this high-risk patient, 18-fluoro-deoxyglucose positron emission tomography scanning is not the ideal imaging modality in patients with MTC, as there is a high false-negative rate. CT of the lungs and liver is a more effective means of identification of distant metastases.

While evaluation for hyperparathyroidism by measuring the serum parathyroid hormone level is indicated in this patient with MEN2A, it is not the most appropriate next step in management. Testing for hyperparathyroidism is recommended prior to surgery because the parathyroid disease can be managed simultaneously with the thyroid cancer, but would not be an appropriate step before evaluating a patient with MEN2A for the presence of pheochromocytoma.

Total thyroidectomy and lateral neck dissection should not be performed until it is confirmed that this patient does not have a coexisting endocrine neoplasm owing to the high intraoperative risk associated with untreated pheochromocytoma. If identified, pheochromocytomas should be surgically removed prior to thyroidectomy.

Genetic counseling is a very important component of the treatment plan for all patients with newly diagnosed MEN2A as first-degree relatives are at high risk for also having the RET mutation. With a nearly 100% penetrance for development of MTC in carriers of RET mutations, referral to a team with experience in the management of these disorders is critical for timely diagnosis and treatment.