Fine needle aspiration cytology of small cell neuroendocrine carcinoma of the breast. A case report.

BACKGROUND: Neuroendocrine tumors, usually small cell (oat cell) carcinomas, are almost always primary in the lungs and are highly malignant. Similar tumors have recently been described to occur in various extrapulmonary sites, such as the uterine cervix and prostate. We report a primary neuroendocrine carcinoma of the breast in a female first diagnosed by fine needle aspiration biopsy (FNAB). Search of the literature revealed only three other reports of small cell carcinoma of the breast, one in a male and two in a female, thus making this the third documented case of neuroendocrine carcinoma of the breast in a female. CASE: A 45-year-old, black female presented with a firm, nontender mass at the tail of her left breast. FNAB showed atypical epithelial cells with pale nuclei and inconspicuous nucleoli. An excisional biopsy performed one week later showed microscopically a predominantly solid and syncytial pattern of small cells that appeared spindly in places. It had a high mitotic count, and the stroma was rich in lymphocytes and plasma cells. Immunohistochemical and ultrastructural studies confirmed the diagnosis.
CONCLUSION: Small cell (neuroendocrine) mammary carcinoma is a rare entity but does occur and can be diagnosed by FNAB. It does not differ essentially from other mammary neoplasms with regard to prognosis.