Atypical acinar cell nodules of the human pancreas

The earliest morphological evidence of altered growth potential of pancreatic acinar cells of the rats treated with carcinogen, such as azaserine, is the development of nodules of atypical acinar cells, some of which are considered to appear, eventually, as acinar cell carcinomas. On the other hand, there exist nodular lesions in the human pancreas, which are similar to atypical acinar cell nodules of the rats, in the sense of nodularity, multiplicity, size, and cytological features, such as pale cytoplasm. To clarify the plausibility of the human nodular lesions as a precursor of acinar cell carcinoma of the pancreas, light and electron microscopical studies were performed, using pancreases of 115 semi-consecutive series of autopsy cases and 20 surgical cases. Multiple nodular lesions were found in 3 autopsy cases and one surgical cases. Ultrastructurally, markedly dilated cysterna of rough-surfaced endoplasmic reticulum and intracisternal granules were the most prominent characteristics of the atypical cells of the nodules. These features are neither reported in chemically induced atypical acinar cell nodules and carcinomas nor in human acinar cell carcinomas. The human lesions were considered to be of degenerative nature rather than neoplastic.