c-kit expression in small cell carcinoma of the urinary bladder:: prognostic and therapeutic implications

The prognosis for small cell carcinoma of the urinary bladder is poor, and strategies for improved therapy are needed. Targeted therapy against the c- kit proto- oncogene has been successful in the management of gastrointestinal stromal tumor. We investigated the expression of c- kit in 52 cases of small cell carcinoma of the urinary bladder. Specimens with more than 10% of cells demonstrating strong membrane staining were considered to have positive immunostaining for c- kit. c- kit expression was detected in 21 of 52 specimens from these patients. Among the 21 specimens, seven had less than 10% staining, and were considered to be negative. Nine had 11 - 50% staining, and five had more than 50% staining. Overall, 14 of 52 ( 27%) small cell carcinomas of the urinary bladder were positive for c- kit expression. During a median follow- up of 11 months, 60% of the patients died of bladder cancer. No association was found between c- kit expression and survival or other clinicopathologic parameters. Five- year cancer- specific survivals for c- kit- positive and c- kit- negative tumors were 9 and 15%, respectively ( P = 0.36). A significant proportion ( 27%) of small cell carcinomas of the urinary bladder expressed c- kit, suggesting that it may prove useful as a therapeutic target in small cell carcinoma of the urinary bladder.