Small cell carcinoma of the urinary bladder—Immunocytochemical study c-kit

Objective : Small cell carcinomas (SmCCs) of the urinary bladder are a rare entity with an incidence of less than 1% of all malignant neoplasms of the urinary tract. Primary SmCC of the bladder must be distinguished from invasive papillary urothelial carcinoma (IPUC) or malignant lymphoma. Immunohistochemistry of the histological specimen has been recognized as being very useful in the diagnosis of SmCC. Furthermore, recent immunohistochemical studies showed that the KIT protein is expressed in a significant percentage of bladder SmCCs. Study Design : Four cases of bladder SmCC experienced at our hospital during the period 1988-2013 were retrospectively studied. We analyzed the clinical information, cytomorphological features, and immunohisto/cytochemical findings. Result : The cytomorphological features of voided urine specimens closely resembled those of all other SmCC cases seen up to the present. The tumor cells of all our cases were immunocytochemically positive for c-kit. Two (50%) of them were strongly positive, one (25%) was moderately positive and one (25%) showed weak immunoreactivity. Conclusion : Our findings showed that a significant proportion of SmCCs of the urinary bladder expressed c-kit, suggesting that immunocytochemistry to test for c-kit may be useful in the cytodiagnosis of bladder SmCC.