Small cell carcinoma of the renal pelvis: a clinicopathological, morphological and immunohistochemical study of 2 cases.

Two women, 62 and 66 years old, with combined small cell carcinoma and transitional cell carcinoma of the renal pelvis are reported. The clinical picture was similar to that seen in conventional transitional cell carcinoma. A brief review of the literature indicates that in the urinary tract, small cell carcinoma occurs most commonly in the bladder and is exceedingly rare in the renal pelvis; only 2 cases have been reported previously. The morphological spectrum of the small cell carcinomatous component is similar to that seen in lung tumors. Neuroendocrine differentiation of the small cell carcinoma component was supported by a positive immunoreaction to neuron-specific enolase in both cases and to synaptophysin in 1. One patient died with metastases 8 months after diagnosis, and 1 was alive with clinical evidence of lymph node metastases and contralateral papillary transitional cell carcinoma of the renal pelvis 16 months after diagnosis.