DIFFERENTIATION OF COLONIC METAPLASIA FROM ADENOCARCINOMA OF URINARY-BLADDER

Colonic metaplasia and primary bladder adenocarcinoma are relatively u ncommon entities that can have similar gross clinical appearances, Exa mples of colonic metaplasia histologically mimicking cancer have only rarely been reported. We retrospectively analyzed 38 cases of cystitis glandularis (18 cases of colonic metaplasia), 12 cases of adenocarcin oma of urinary bladder (two well-differentiated, WDA), and one in situ adenocarcinoma from the surgical pathology files of Johns Hopkins Hos pital. Nine patients with colonic metaplasia had widespread lesions. T wo showed superficial muscularis propria involvement, mimicking adenoc arcinoma; one of these cases had been diagnosed as infiltrating WDA at both an academic center and a community hospital. Dissecting mucin po ols were focally seen in four cases of widespread colonic metaplasia, also mimicking cancer, One of the nine cases showed minimal cytologica l atypia, but no cases showed mitoses or signet ring-cells. Distinguis hing WDA from colonic metaplasia was the finding in WDA of infiltrativ e architectural pattern (two of two), extensive muscle invasion (two o f two), moderate anaplasia (one of two), mitotic figures (two of two), and extensive mucinous pools (one of two). The diagnosis of adenocarc inoma in situ was based on anaplasia. Clinically, colonic metaplasia m ay resemble cancer, Histologically, colonic metaplasia may mimic cance r based on extensive involvement of the lamina propria, focal mucinous pools, focal muscularis propria involvement, focal mild cytological a typia, and rare mitoses. Despite overlapping features with colonic met aplasia, the diagnosis of WDA is based on the greater degree and exten t of these atypical findings in cancer, Copyright (C) 1997 by W.B., Sa unders Company.