Primary neuroendocrine tumors of the breast: two case reports and review of the literature

Background Neuroendocrine carcinomas mainly affect the bronchopulmonary and the gastrointestinal systems. Breast localizations are very rare. They represent less than 0.1% of all breast cancers. A definitive diagnosis relies on histological and immunohistochemical examinations. Case presentation Case 1 We report a case of primary neuroendocrine carcinoma of the breast in a 71-year-old Arabic woman who presented with a 3 cm palpable and mobile tumor of the right breast. Clinical and radiological assessment excluded any other primary tumor. Radical mastectomy and axillary lymph node resection were performed. A histopathological examination disclosed the diagnosis of primary breast neuroendocrine tumors, with negative surgical margins and lymph nodes (18 N-/18 N). The tumor cells were positive for neuroendocrine markers, a weak Ki-67 proliferation index and negative Her2/neu. Our patient received adjuvant hormonal treatment with anti-aromatase for 21 months. She is on regular follow-up, and she remains free of disease to date. Case 2 A 48-year-old Arabic woman consulted for a right breast nodule. She underwent lumpectomy with right axillary lymphadenectomy. The diagnosis was breast neuroendocrine tumor. Systemic treatment was proposed, but she was lost to follow-up. She consulted 1 year later for a mass in the same breast. A histological and immunohistochemical examination of a mammary biopsy was consistent with a recurrence of the previous neuroendocrine tumor. A radiological assessment showed a large mass in her right breast, ipsilateral axillary lymphadenopathies, and hepatic and pulmonary metastases. She received first-line metastatic chemotherapy, with good clinical and radiological improvement. She refused the mastectomy and was given hormone therapy. One year later, the tumor expanded clinically and radiologically, and she underwent second-line metastatic chemotherapy, with good clinical progress and radiological stability, and she then underwent maintenance hormonal therapy. Conclusion Due to the rarity of primary breast neuroendocrine tumors, no standard therapy exists and the prognosis remains difficult to determine. Studies, including larger series, are needed in order to understand the biological behavior of these tumors.