Microcystic transitional cell carcinomas of the urinary bladder. A report of four cases.

Four transitional cell carcinomas of the urinary bladder that on microscopic examination were found to have cysts are described. The tumors occurred in patients from 35 to 69 years of age and were all deeply invasive; two were grade 2 and two grade 3 (of three grades). Cysts were prominent in all of the cases and predominated in one of them. In the latter case, the cysts caused major problems in interpretation. The cysts, which usually were round to oval and were as large as 1.2 mm, were of varying sizes. They usually were lined by transitional cells or low columnar cells showing mucinous differentiation; occasionally they were lined by a single layer of flattened cells or the lining epithelium was denuded. Elongated, irregular branching spaces also were present. Recognition of these tumors is facilitated by their association with typical transitional cell carcinoma, but when the cysts predominate, awareness of this change may be essential in establishing the diagnosis, particularly in a biopsy specimen.