Neuroendocrine Tumor of the Breast in a Young Woman With MEN2A Syndrome

Breast neuroendocrine tumors (BNETs) comprise < 1% of breast cancers. The coexistence of BNET with MEN2A syndrome has not been previously reported. We present a unique case of BNET in a young woman with MEN2A syndrome. A 20-year-old woman presented with headaches, nausea, and palpitations. Evaluation revealed bilateral adrenal nodules and thyroid mass with elevated calcitonin and metanephrines. Genetic testing confirmed MEN2A syndrome (RET p.C634R mutation). She underwent adrenalectomy and thyroidectomy for pheochromocytoma and medullary thyroid carcinoma. Incidental PET imaging identified a 14 mm breast mass. Biopsy revealed grade 2 ER+/PR+/HER2-BNET. Breast-conserving surgery showed stage I disease with negative lymph nodes. BNETs carry worse prognosis than conventional breast cancers. The RET C634R mutation requires lifelong surveillance for recurrent endocrine malignancies. Whether this mutation influences BNET behavior remains unknown. This case highlights diagnostic complexities of BNET in MEN2A syndrome, emphasizing comprehensive surveillance in hereditary endocrine syndromes and multidisciplinary management for rare neuroendocrine presentations. Teaching Points • Primary breast neuroendocrine tumors (BNETs) are rare in MEN2A syndrome patients. • MEN2A syndrome from RET mutations predisposes to medullary thyroid carcinoma. • Multidisciplinary collaboration is essential for complex hereditary tumors. • Genetic testing should be performed in all medullary thyroid cancer patients. • Sequential surgical management with alpha blockade minimizes complications.