The packet does not certify a gene list, inheritance pattern, or molecular mechanism for this condition, so its genetic basis is not established here and no genes are named.

The definition states that approximately 10% to 20% of cases are familial. The GeneReviews MEN2 chapter reports that about 20%-30% of all individuals with MTC have a germline pathogenic variant, that approximately 6%-7% of individuals with simplex MTC (no known family history of MTC or other endocrine disease) had one, and that a somatic pathogenic variant without a germline variant is identified in 40%-50% of MTCs. These figures come from that chapter's discussion of a hereditary syndrome and are attributed to it. The chapter also describes incomplete penetrance of some variants in the MEN2 setting and notes that family history may appear negative because of unrecognized disease in relatives, reduced penetrance, early parental death, or late onset.

The packet lists no standalone diagnostic criteria beyond the definition; the following comes from the GeneReviews MEN2 chapter and describes MTC in that syndrome.

GeneReviews describes MEN2A as suspected in individuals with medullary thyroid carcinoma, pheochromocytoma, or parathyroid adenoma/hyperplasia, and familial medullary thyroid carcinoma as diagnosed clinically in families with two or more individuals with MTC in the absence of those other tumors. MTC and C-cell hyperplasia are described as suspected when plasma calcitonin is elevated, measured at baseline and after intravenous calcium stimulation; pentagastrin is also described as a secretagogue, available in Europe and limited in the United States. The packet's orphan drug records list pentagastrin with DESIGNATED status as a diagnostic; designation is not an approval. Histologically, MTC is diagnosed when nests of C cells extend beyond the basement membrane and infiltrate thyroid follicles, with calcitonin immunohistochemistry as an adjunct. The chapter describes evaluation for metastatic disease using CT of the chest and abdomen and, with nodal disease or high calcitonin, MRI of the liver. Genetic confirmation is described there as one route to the MEN2 diagnosis, not a universal standard for all MTC.

The packet definition states that surgery is the preferred treatment for both primary lesions and recurrences, and that the carcinoma is generally not very sensitive to radiation and almost unresponsive to chemotherapy.

Two FDA records in the packet have market status ACTIVE (currently FDA-approved): RETEVMO (selpercatinib, NDA, approved 2024-04-10) and CAPRELSA (vandetanib, NDA, approved 2011-04-06); the packet does not state their labeled indications. The orphan drug records also list Nexavar (sorafenib, Bayer HealthCare Pharmaceuticals, Inc.) with status APPROVED and an orphan indication that includes medullary thyroid cancer, and pentagastrin as DESIGNATED only.

The GeneReviews MEN2 chapter describes standard treatment for MTC as surgical removal of the thyroid with lymph node dissection, with external beam or intensity-modulated radiation described for incomplete resection or extrathyroidal extension with positive margins. For metastatic MTC it describes multikinase inhibitors (vandetanib, cabozantinib), RET-selective inhibitors (selpercatinib, pralsetinib), and pembrolizumab for tumor mutational burden-high disease that progressed on prior treatment, and states that kinase inhibitors have improved progression-free survival in some persons. The packet does not certify FDA status for agents named in GeneReviews that lack an ACTIVE record. For hereditary MEN2, GeneReviews describes prophylactic thyroidectomy as the primary preventive measure for individuals with an identified germline pathogenic variant, thyroid hormone replacement after thyroidectomy, and evaluation for pheochromocytoma before surgery, with supportive care involving endocrinology, endocrine surgery, and medical genetics.

The packet does not certify survival statistics or a structured prognosis, and none are given here. The definition notes nodal involvement at diagnosis in the majority of cases.

The GeneReviews MEN2 chapter reports that diarrhea with a plasma calcitonin of 10 ng/mL or higher implies a poor prognosis, and that approximately 50% of individuals with MTC who underwent total thyroidectomy and neck nodal dissections have recurrent disease. It describes variable expression in the MEN2 setting, including one variant with MTC at age five years and fatal metastatic MTC at age 12 years in some individuals but no clinical evidence of MTC at age 86 years in others. These observations describe the literature on the hereditary setting and are not individual prognostic statements.

The packet lists 49 active ClinicalTrials.gov records for this condition, with a search link; several carried records concern other tumor types. Records titled for medullary thyroid cancer include NCT01660984, a National Cancer Institute natural history study (ACTIVE_NOT_RECRUITING, started 2012-07-30); NCT04216732, an M.D. Anderson Cancer Center natural history study (RECRUITING, 2020-01-10 to 2028-09-01); and NCT07142005, an M.D. Anderson study of an educational tool (RECRUITING, 2025-08-15 to 2028-03-31). The packet's intervention summary lists drug therapy, biologic therapy, procedural, and other interventions, with no gene therapy trials flagged.

The GeneReviews MEN2 chapter describes trials of multikinase inhibitors (sorafenib, sunitinib, regorafenib) and immune checkpoint inhibitors (pembrolizumab, nivolumab, ipilimumab) as under way. The packet's research digest classifies 83 publications, most commonly case reports or case series. No patient organizations are certified in this packet.