Signet ring cell carcinoma in a Schistosoma-infested bladder: case report and histochemical study.

A case of signet ring cell carcinoma of the urinary bladder with concomitant Schistosoma haematobium infection is reported with a histochemical study of mucous secretion. This rare kind of tumor differentiation in Schistosoma-related neoplasms may suggest that the tumor-promoting stimuli, acting on reserve cells of bladder epithelium, do not determine the tumor differentiation pattern as strictly as currently thought.