Rare breast and subcutaneous metastases from pancreatic neuroendocrine tumor: a case report

BACKGROUND: Neuroendocrine tumors are a group of rare neoplasms, and the pancreatic neuroendocrine tumors (PNETs) represent only 1–2% of all pancreatic malignant tumors. The most common sites of these tumors include the gastrointestinal tract, lung, adrenal gland, and thyroid gland. Moreover, the most common sites of PNET metastases are the lymph nodes, liver, spleen, and bone. CASE SUMMARY: A 40-year-old woman with pT3N1 PNET underwent surgical excision of the lesion (12 cm, at the level of the pancreatic body and tail). Postsurgical treatment included chemotherapy and radiation, both of which the patient showed a good tolerance for. After a 12-month disease-free interval, however, the patient reported the development of a lesion in her left breast and a small lesion in the left posterior region of her neck. The lesions were surgically excised, and the histological findings characterized both as pancreatic neuroendocrine metastatic poorly differentiated neoplasms (G3). A re-staging CT scan showed multiple metastases in the left axillary, clavicular, and latero-cervical lymph nodes, as well as diffuse osteolytic-osteoblastic bone metastases, almost mimicking the behavior of a primitive breast tumor. CONCLUSION: This case of breast and subcutaneous metastases from PNET should prompt awareness of potential metastatic lesions in unusual locations.