Case report of primary small cell neuroendocrine breast cancer

Primary neuroendocrine cancer of the breast (NECB) is an extremely rare tumor. In 2003, the World Health Organization (WHO) recognized this category with three well-described subtypes: small cell, large cell, and carcinoid-like carcinoma; very few peer-review publications based on the WHO definition were encountered in the literature, and we conducted a literature search to investigate the reported incidence, diagnosis, prognosis, hormone receptor status, and treatment options for this rare tumor. Confirming the breast as an origin of neuroendocrine tumor represents a challenge. The diagnosis is mainly dependent on the exclusion of other extra-mammary organs based on clinical, radiological, and pathological data. Primary neuroendocrine carcinoma of the breast is rare - only about 30 cases have been reported in literature. Immunohistochemical examination showing expression of chromogranin and/or synaptophysin confirms evidence of neuroendocrine differentiation. Usually foci of neuroendocrine differentiation can be seen in breast carcinoma and are reported to be present in about 2–5% of breast cancer cases. Here, we report a case of breast carcinoma in which most of the areas studied on the tissue section showed neuroendocrine differentiation. Primary neuroendocrine carcinoma of the breast is a group that exhibits morphological features similar to those of neuroendocrine tumors of both the gastrointestinal tract and the lung. CASE PRESENTATION: We report the case of a 50-year-old Caucasian woman with primary small cell neuroendocrine cancer of the breast, which we characterized with immunohistochemical techniques. A palpable and mobile 3.0 cm tumor was located in the upper-outer quadrant of her right breast. After pathological confirmation the patient underwent 8 cycles of chemotherapy, and subsequent radical mastectomy with axillary lymph node resection were performed. Microscopically, the tumor consisted predominantly of a diffuse proliferation of small oat cells. The tumor cells were positive for neuroendocrine markers; 21 of 30 lymph nodes were metastatic. Local recurrence with multiple lung metastases developed only 5 weeks after surgery, despite of the transient tumor regression achieved by chemotherapy. This case reinforces the importance of an early correct diagnosis and the standardization of a treatment regimen for this very rare tumor. A correct treatment needs to be chosen.