Should asymptomatic individuals without risk factors be screened for medullary thyroid carcinoma, and what screening is recommended for high‑risk patients such as RET mutation carriers, those with a family history of medullary thyroid carcinoma, or multiple endocrine neoplasia type 2?

Screening for Medullary Thyroid Carcinoma

Asymptomatic Individuals Without Risk Factors

Routine screening for medullary thyroid carcinoma is not recommended in the general asymptomatic population. 1

• The NCCN explicitly does not recommend routine measurement of basal serum calcitonin concentration for evaluating patients with nodular thyroid disease because of the expense incurred by screening all thyroid nodules to find only a few cases of MTC, the lack of confirmatory pentagastrin stimulation testing, and the resulting need for thyroidectomy in some patients who actually have benign thyroid disease. 1

• While approximately 3% of patients with nodular thyroid disease will have an increased serum calcitonin level when measured with a sensitive immunometric assay, and 40% of these patients will have MTC at thyroidectomy, the cost-benefit ratio does not support population-wide screening. 1

• Sporadic MTC is typically discovered incidentally after fine-needle aspiration (FNA) of a solitary thyroid nodule, not through systematic screening programs. 1

High-Risk Patients: RET Mutation Carriers and Family History

All individuals with known RET proto-oncogene mutations or a family history of MTC/MEN 2 syndromes require immediate genetic testing and aggressive surveillance, not calcitonin screening. 1, 2

Genetic Testing Protocol

• All patients with newly diagnosed clinically apparent sporadic MTC should undergo RET proto-oncogene mutation testing, as approximately 6% carry a germline mutation, allowing identification of previously unrecognized familial cases. 1, 2

• All first-degree relatives of patients with confirmed hereditary MTC, MEN 2A, or MEN 2B must undergo RET genetic testing to identify disease carriers long before clinical symptoms develop. 1, 2

• Mutations in the RET proto-oncogene are found in at least 95% of kindreds with MEN 2A and 88% of familial MTC. 1

• The traditional approach of stimulating calcitonin secretion with pentagastrin or calcium infusion is no longer recommended because elevated calcitonin is not a specific or adequately sensitive marker for MTC, and pentagastrin is no longer available in the United States. 1

Management Based on RET Mutation Status

For confirmed RET mutation carriers, prophylactic total thyroidectomy should be performed based on mutation-specific risk stratification, not screening tests:

MEN 2B (Highest Risk: Codon 918,883, or Compound Heterozygous Mutations)

• Total thyroidectomy should be performed within the first year of life, ideally before age 1. 1
• Basal calcitonin level, CEA, and neck ultrasound should be obtained before surgery. 1
• Pheochromocytoma screening is mandatory before any surgical intervention. 1, 3

MEN 2A (Codons 609,611,618,620,630,634,768,790,791,804, or 891)

• Total thyroidectomy should be performed by age 5 years, or when mutation is identified if diagnosed at an older age. 1
• For lower-risk RET mutations (codons 768,790,791,804,891), prophylactic thyroidectomy may be delayed provided the annual basal calcitonin measurement is normal, the annual ultrasound is unremarkable, there is no history of aggressive MTC in the family, and the family is in agreement. 1
• Measure serum intact parathyroid hormone and calcium to screen for hyperparathyroidism. 1
• Pheochromocytoma screening is mandatory before any surgical intervention. 1, 3

Familial MTC (Same RET Mutations as MEN 2A)

• Follow the same thyroidectomy timing as MEN 2A based on specific mutation. 1
• Annual surveillance includes basal calcitonin, CEA, pheochromocytoma screening, and neck ultrasound. 1

Critical Pre-Operative Screening for Hereditary Cases

Before proceeding to thyroidectomy in any RET mutation carrier, the following screening is mandatory:

• Pheochromocytoma must be diagnosed and treated before thyroid surgery to avoid hypertensive crisis during surgery. 1, 3
• Screen with plasma metanephrines and normetanephrines (sensitivity approximately 100%) or 24-hour urine collection for metanephrines. 3
• For MEN 2A, measure serum calcium and intact parathyroid hormone. 1
• Perform neck ultrasound to evaluate for thyroid or nodal abnormalities. 1, 2

Ongoing Surveillance for RET Mutation Carriers

Annual screening for pheochromocytoma (MEN 2A and 2B) and hyperparathyroidism (MEN 2A) should be performed lifelong. 1, 3

• For some RET mutations (codons 768,790,804, or 891), less frequent screening may be appropriate. 1
• Post-thyroidectomy surveillance includes serum calcitonin and CEA every 6-12 months. 1

Common Pitfalls

• Never perform thyroidectomy before excluding and treating pheochromocytoma in hereditary cases, as this can cause fatal intraoperative hypertensive crisis. 1, 3

• Do not rely on calcitonin screening alone in known RET mutation carriers—genetic testing dictates timing of prophylactic surgery, not biochemical markers. 1, 2

• Approximately 6% of apparently sporadic MTC cases harbor germline RET mutations, so genetic testing should be offered to all MTC patients regardless of family history. 1, 2

• Referral to a surgeon and team experienced in pediatric thyroid surgery is advised for very young children undergoing prophylactic thyroidectomy. 1