Carcinoma of the urinary bladder with a lymphomatous appearance.

We present the first report of bladder carcinoma that demonstrates a mixture of two distinct histological patterns resembling malignant lymphoma. The patient was a 79-year-old man. One of the histological patterns was a diffuse growth of monomorphic carcinoma cells, and the other was a dense lymphoplasmacytic infiltrate, obscuring the carcinoma. The tumor cells showing both patterns expressed cytokeratin and epithelial membrane antigen, but not lymphoid markers. Careful immunohistochemical evaluation should be done when diagnosing urinary bladder carcinomas resembling lymphomas (other than primary lymphomas).