Carcinoma in situ of the gallbladder with superficial extension into the Rokitansky-Aschoff sinuses and mucous glands.

Twenty-four cases of carcinoma in situ of the gallbladder encountered over the past 29 years were evaluated histopathologically. Macroscopic classification disclosed 12 protruding types and 12 superficial types (7 elevated types and 5 flat types). Histologically, 18 cases had papillary growth and 6 had tubular patterns. Epithelial dysplasia of varying degrees was observed around the carcinoma in situ in all except one case and was seen more extensively in superficial type cases, although it was often hard to distinguish dysplasia from carcinoma in situ in some cases. Metaplasia of the mucous glands was observed in 20/24 cases (83.3%). Superficial extension of carcinoma in situ into the Rokitansky-Aschoff sinuses (located below the muscle layer) was observed in 11 cases (45.8%), and extension into the mucous glands was seen in 8 cases (33.3%). These results indicate that it is very important to be able to differentiate invasive carcinoma from cases with superficial extension of dysplasia and/or carcinoma in situ deep into the mucous glands or Rokitansky-Aschoff sinuses. Histological assessment should also be conducted carefully while considering these factors.