Dysplasia and carcinoma in situ of the exocrine pancreas.

To clarify the morphological aspect of precancerous and related lesions of the exocrine pancreas, histological studies were carried out according to a systematized protocol. The pancreas, its head, body and tail including the papilla and adjacent duodenal mucosa and the distal common bile duct from 206 unselective autopsy cases, excluding those of pancreatic carcinoma, were systematically examined. Histological grading of dysplasia was performed based on structural (SAT) and cellular (CAT) atypia which were evaluated by coding 0, 1, 2, and 3. Dysplasia and related changes were encountered in 75 cases (36%) including 6 carcinoma in situ. 1 occult invasive carcinoma (3%), and 10 moderate to severe dysplasias (5%). Of these 75, 46 were associated with parenchymal fibrosis but 29 were not. Simple epithelial hyperplasia and squamous metaplasia were observed in 90 cases (44%), and 34 cases (17%), respectively. Among 90 hyperplasias, 61 were associated with fibrosis, but 29 were not. The incidence of these epithelial abnormalities was higher than that reported in the previous papers. Both dysplasia and hyperplasia showed characteristic age, sex and site preponderances. An intimate relationship between dysplasia and chronic pancreatitis, and possible transition from dysplasia into carcinoma in situ and then invasive cancer were emphasized.