Histogenesis of epithelial neoplasms of human gallbladder II. Classification of carcinoma on the basis of morphological features.

The material consisted of 83 gallbladders with primary carcinoma. Non-malignant bordering mucosa was present in 37 specimens and in 34 of these (92%) it was metaplastic, mostly (78.4%) of antral type. In all but one case the bordering epithelium contained dyplasias of different degrees and thus the dysplasia had manifested in metaplastic epithelium. According to their degree of differentiation, the carcinomas were divided in three groups. In groups 1 and 2 the structure was intestinal. Group 1, which had the highest degree of differentiation, contained papillary and glandular structures. Group 2 contained similar glandular structures but, unlike group 1, no goblet and no enterochromaffin cells. In group 3 (anaplastic carcinomas) the mode of growth was infiltrative or solid. The amount of mucin decreased with the degree of differentiation. Histochemically, there were no differences between the groups, but the mucin was mainly non-sulphated acid mucin as in the metaplastic and dysplastic areas surrounding the tumour, thus differing from the normal gallbladder epithelium containing sulphated acid mucin. In 52 cases it was possible to investigate the superficial part of the tumour. The carcinoma structure was of a high degree of differentiation (group 1) in 29 (55.8%) cases, which all had structures of group 2 in the deeper layers. These results indicate that the structure of the carcinoma is not permanent, it dedifferentiates at the deeper invasive layers. In only two cases (3.8%) was the anaplastic structure of group 3 already on the surface without the intermediate stages of groups 1 and 2.