mucosal neuromas
Summary
Mucosal neuromas are benign, painless, pink/flesh-colored nodules composed of proliferated nerve tissue found on the lips, tongue, and buccal mucosa. They are a classic hallmark of Multiple Endocrine Neoplasia type 2B (MEN2B), often one of the earliest clinical signs. Recognition is critical for prompt genetic testing and early thyroidectomy due to aggressive medullary thyroid carcinoma risk.
Detail
Mucosal neuromas result from a germline gain-of-function mutation in the RET proto-oncogene (specifically M918T), which drives both neural tissue overgrowth and oncogenic transformation in endocrine tissues. They typically appear as multiple, small, glistening, painless bumps on the distal tongue, lips, and buccal mucosa, giving a 'bumpy lip' appearance, and may also involve the eyelids (causing thickened, everted eyelids) and conjunctiva.
Clinically, mucosal neuromas are pathognomonic for MEN2B, a syndrome that also includes medullary thyroid carcinoma (nearly 100% penetrance, often aggressive and presenting in infancy/early childhood), pheochromocytoma (~50%), and a marfanoid habitus with skeletal abnormalities (pes cavus, pectus excavatum, joint laxity) and gastrointestinal dysfunction (megacolon, constipation) due to intestinal ganglioneuromatosis.
Because medullary thyroid carcinoma in MEN2B is particularly virulent, early recognition of mucosal neuromas should prompt RET genetic testing and consideration of prophylactic thyroidectomy within the first year of life, distinguishing management urgency from MEN2A (where prophylactic thyroidectomy can be delayed). Elevated calcitonin and CEA are used for surveillance of medullary thyroid carcinoma. Unlike neurofibromas (seen in NF1) or Schwannomas, these are true neuromas—proliferations of nerve fascicles with perineurium—not neoplastic transformation of Schwann cells.
Sources
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
- UpToDate: Multiple Endocrine Neoplasia Type 2
- Goldman-Cecil Medicine
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