Allograft pancreas: pale acinar nodules.

Microscopic pale-staining acinar nodules were characterized in native pancreas in the 1980s under a variety of names but have been infrequently reported since. We retrospectively studied the frequency and characteristics of pale acinar nodules in allograft pancreas biopsies, as compared to a sampling of native pancreas specimens at our center. Pale acinar nodules were present in 13% (9/69) of allograft biopsies from 22% (7/32) of transplant patients, and 23% (5/22) of native pancreas surgical specimens, although more nodules per pancreas area were present in allograft needle biopsies. Acinar nodules had size of 100 to 700 μm, were periodic acid-Schiff pale, were synaptophysin negative, stained more weakly with keratin CAM 5.2 compared to surrounding parenchyma, and had a low proliferative rate. Ultrastructural evaluation revealed paucity of zymogen granules with dilated cistern-like structures. In our experience, pale acinar nodules have similar features in allograft and native pancreas specimens, yet remain of uncertain etiology and significance.