Primary neuroendocrine breast cancer—an unusual occurrence

Primary breast neuroendocrine neoplasms (BNENs) are a rare form of breast cancer, accounting for less than 0.1% of all breast malignancies. These neoplasms have a similar clinical presentation as conventional breast carcinomas, differing mainly in their histopathology and expression of neuroendocrine (NE) markers, chromogranin and synaptophysin. Owing to their rarity, current knowledge of these tumours comes mainly from corroborative case reports or retrospective case series. There is hence a lack of randomised data on the treatment of these entities and current protocol suggests similar treatment as that of conventional breast carcinomas. We report the case of a 48-year-old with a breast mass, which on further work-up was diagnosed as locally advanced carcinoma breast, that required a mastectomy and axillary node dissection on the same side and revealed NE differentiation on histopathological examination. Hence, immunohistochemical staining was indicated which confirmed NE differentiation. We discuss the current knowledge on incidence, demographics, diagnosis, histopathological and staining characteristics, prognostic factors and treatment modalities of BNENs.