[A Case of Breast Neuroendocrine Carcinoma].

A 73-year-old woman visited our hospital with the chief complaint of a mass in the left breast. Breast ultrasonography revealed a hypoechoic area in the left breast. A core needle biopsy showed the proliferation of solid tumor cells. Immunohistochemistry indicated strongly positive expression of E-cadherin, synaptophysin, and chromogranin A. We then diagnosed her with breast neuroendocrine carcinoma. The expression of estrogen receptor(ER)and progesterone receptor(PgR)were also strongly positive, and the expression of human epidermal growth factor receptor 2(HER2)was negative. Computed tomography( CT)and bone scintigraphy revealed no metastasis. Simple mastectomy of the left breast and sentinel lymph node biopsy were performed. Final pathological examination of the tumor also led to the diagnosis of breast neuroendocrine carcinoma(T2N0M0, StageⅡA, Luminal A-like). After surgery, endocrine therapy is planned, considering the breast cancer subtype. Breast neuroendocrine carcinoma is rare. It is important to consider the possibility of metastasis from other organs to the breast.