How do I diagnose Primary neuroendocrine tumor of the breast

Primary neuroendocrine tumor of the breast is a rare condition. Although 20-30% of primary breast cancers show neuroendocrine differentiation to some degree, according to the WHO classification, at least 50% of the tumor cells have to be positive with at least one neuroendocrine immunohistochemical marker to establish a diagnosis of neuroendocrine tumor of the breast while clinically excluding other primary sites and a metastatic nature. Due to the low prevalence of this disease our understanding of its development, prognosis and effective therapy is limited. Up to date there are 125 cases reported in the English and non-English literature, now including our own case as well. We report a case of a 75 years old female. The patient presented with a 2 cm large mobile nodule in the upper outer quadrant of the left breast. Lumpectomy was performed based on fine needle aspiration cytology with a positive result showing malignant proliferation. Examination of the surgical specimens revealed neuroendocrine differentiation in approximately 90% of the tumor cells. Immunohistochemical studies and additional imaging studies revealed no other primary