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.
Keywords: breast cancer; dissemination; primary small cell neuroendocrine breast cancer; treatment.