Small cell carcinoma of the kidney - A case report and review of the literature

Small cell carcinoma is a malignant tumor composed of small cells with a di ffuse growth pattern. It has immunohistochemical and ultrastructural featur es of both neuroendocrine and epithelial neoplasms. These tumors constitute 10% to 20% of malignant tumors in the lung, which is their most frequent s ite. They have been described in other extrapulmonary sites, where they are defined using the same criteria as used in the lung. These tumors are rare ly found in the genitourinary tract. Fewer than 30 cases have been reported in the kidney. The differential diagnosis mainly includes other small roun d cell tumors and metastatic small cell lung carcinoma. We present and disc uss a primary small cell carcinoma of the kidney (to our knowledge the 9th to be reported in the literature), which we studied with light microscopy, immunohistochemistry, electron microscopy, and, for the first time, flow cy tometry.