Neuroendocrine breast carcinoma metastatic to renal cell carcinoma and ipsilateral adrenal gland.

We report on a 60-year-old woman with neuroendocrine carcinoma of the left breast metastasizing to renal cell carcinoma (RCC) of the left kidney and to adrenal gland. A yellow, well-circumscribed tumor, 11 cm in largest diameter and limited to the kidney, was found. Histopathology revealed RCC with foci of neuroendocrine differentiation. Solid sheets of hyperchromatic epithelioid cells with high mitotic activity were found between typical clear cells of RCC. These cells were CAM5,2 and E-cadherin focally positive, synaptophysin and NSE weakly positive, CK19 moderately positive, and AE1-AE3 and EMA strongly positive. Chromogranin A, CD10, CK 14, CK 20, HER2 (score 1+), vimentin, and HMB45 were negative. The left adrenal gland contained multiple, separate foci of a tumor composed of neuroendocrine components. Because of the biphasic tumor in the kidney, extensive clinical examination and further analyses were recommended. Tumor in the left breast was revealed. Two months later, the patient underwent mastectomy with axillary lymph node dissection. The tumor was histologically and immunohistochemically similar to the neuroendocrine component within RCC. All axillary nodes were positive. To our knowledge, this is the first case of neuroendocrine breast carcinoma with metastasis to renal cell carcinoma and ipsilateral adrenal gland.