Histogenesis of gallbladder carcinoma from investigation of early carcinoma and microcarcinoma.

Carcinomas of the gallbladder can be grossly divided into two types: carcinoma in adenoma (CIA) and carcinoma without adenoma (CWA). The histogenesis of both types of gallbladder carcinoma (CIA and CWA) was investigated in association with metaplastic changes in 35 early carcinomas larger than 5 mm in diameter and 16 microcarcinomas up to 5 mm in largest diameter. In five early CIAs and two micro-CIAs, the carcinoma was surrounded by the adenoma, and the areas of both carcinoma and adenoma mainly showed gastric-type metaplasia (GM). On the other hand, 90% of the other 30 early CWAs showed GM and/or intestinal-type metaplasia (IM) in the tumor, and all of them were surrounded by GM and/or IM. Seven of the other 14 micro-CWAs showed GM and/or IM in the tumor as well as in the surrounding mucosa, and had non-neoplastic metaplastic glands underneath the carcinoma tissue. The remaining seven micro-CWAs showed no or only mild metaplasia in the tumor and were surrounded by proper mucosa without metaplasia. From these data, it is concluded that carcinoma of CIA possibly arises from adenoma mainly with GM, and that CWA originates either from the upper part of the metaplastic mucosa or from the proper mucosa of the gallbladder. In addition, some CWA may undergo secondary metaplastic changes during tumor growth.