Background: Small cell neuroendocrine carcinoma of the breast is a rare tumor with fewer than 30 cases reported in the literature. The reported age of incidence of mammary small cell carcinoma is similar to that of breast carcinoma of the usual types. Case: The clinicopathologic findings of a primary mammary small cell neuroendocrine carcinoma occurring in a 28-year-old female are presented with a review of pertinent literature. She was treated with lumpectomy and sentinel node biopsy as well as chemotherapy and radiotherapy. Conclusions: To the best of our knowledge, this is the youngest patient with primary small cell carcinoma of the breast reported in the English literature, indicating that these tumors occur in a wide age range.