Carcinomas of the urinary bladder with deceptively benign-appearing foci. A report of three cases.

Three men, aged 53 to 77 years, had carcinomas of the urinary bladder characterized by foci with a deceptively benign histological appearance. In two cases, this feature led to a significant delay in establishing the correct diagnosis. The diagnostic difficulty in these cases resulted from the resemblance of foci of infiltrating carcinoma to von Brunn's nests, cystitis glandularis, cystitis cystica, and nephrogenic adenoma, alone or in combination. Features that helped distinguish these foci from benign processes were an irregular distribution, the presence of large numbers of closely packed epithelial aggregates, focal mild to moderate cytologic atypia, and transitions to unequivocal carcinoma. In a third case, the superficial component of a carcinoma closely resembled an inverted papilloma.