Small cell carcinoma of the urinary bladder with hypercalcemia.

This report describes three cases of undifferentiated small cell carcinoma of the urinary bladder. Their light microscopic appearance is closely akin to the small cell carcinoma of lung. The neoplastic cells exhibit few cytoplasmic dense core neurosecretory granules ultrastructurally and immunoreactivity to enolase. Two patients manifested clinically hypercalcemia which is rare in small cell carcinoma in general and, to the best of our knowledge, has not been described in association with bladder small cell carcinoma.