[Primary small cell carcinoma of the kidney: report of a case].

: Primary small cell carcinoma (SCC) of the kidney is an extremely rare neoplasm. The morphological, immunohistological and ultrastructural features are closely akin to primary SCC of the lung. The case of a 38-year-old married male, nonsmoker, with primary small cell carcinoma of the kidney and associated multiple bony metastases is reported. Roentgenographic studies exhibited a tumor mass 3 cm in diameter over the middle portion of the left kidney. A CT scan of the cervical and thoracic spines, and a whole body bone scan displayed multiple osteolytic lesions suggesting multiple bony metastatic lesions. A chest X ray and CT scan of the nasopharynx demonstrated no significant lesions. A complete workup was performed followed by a left nephrectomy. Histologically, the tumor revealed SCC of the kidney. Immunohistochemically, the tumor cells demonstrated immunoreactivity to cytokeratin (CK), neuron-specific enolase (NSE) and produced negative stains to argentaffin, argyrophil, S-100 and chromogranin A. Ultrastructurally, these neoplastic small cells revealed a few cytoplasmic dense-core neuroendocrine-type differentiated secretory granules, measuring 110 to 115 nm in size. Thus, adjuvant therapy, supplemented with chemotherapy and radiotherapy, was employed. The patient was alive and well 6 months after surgery. To the best of our knowledge, there are four documented cases of primary SCC of the kidney. In this article, the light microscopic, immunohistochemical and ultrastructural studies of renal SCC are presented and suggest a renal pelvic epithelial origin of renal SCC. Cognitively renal SCC appears to be an aggressive tumor, regardless of the degree of neuroendocrine differentiation.