[Undifferentiated small-cell carcinoma of the urinary bladder].

We report a case of undifferentiated small cell carcinoma of the urinary bladder in a 64-year-old male patient. Microscopically the tumor was similar to the intermediate type of small cell carcinoma of the lung, with some foci of transitional papillary carcinoma, adenocarcinoma and carcinoma in situ. Small cell carcinoma is seldom encountered in the urinary bladder. It is more aggressive and must be distinguished from poorly differentiated transitional cell carcinoma.