Nonpapillary carcinoma in situ of the urinary bladder. A histopathologic study and mapping of the urothelial lesions.

Three cases of primary nonpapillary carcinoma of the urinary bladder diagnosed by urinary cytology and multiple biopsies were reported. Bladder specimens of two of the patients were totally embedded for step-sections that were mapped after histopathologic study. Atypical hyperplasia and carcinoma in situ with foci of microscopic invasion affected the bladder mucosa and extended continuously to the distal ureters as well as prostatic urethra. Multicentric distribuion of the abnormal epithelium was definite in one case, and the bladder mucosa was extensively denuded in the other case. Metastasis to one of the regional lymph nodes was noted in the remaining one case. The origin of Pagetoid cells occurring in two of the cases is obscure, but we presume that these cells may represent transformed tumor cells showing differentiation toward the surface umbrella cells, or they are derived from Brunn's nests where the cells may gain potential to differentiate to glandular epithelium.