Eosin-shadow method: a selective enhancement of light-microscopic visualization of pancreatic zymogen granules on...

We developed a novel method for enhancing light-microscopic visualization of pancreatic zymogen granules in a selective manner on hematoxylin and eosin-stained sections. By using an absorption filter that transmits light with wavelength from 510 to 550 nm, corresponding to the narrow absorption spectrum of eosin, only eosinophilic tissue and cellular components were remarkably highlighted as distinct shadows against lighter background consisting of basophilic components. Using a pair of mirror sections of the pancreas, immunocytochemistry with anti-amylase antibody confirmed that the shadows observed through the filter represented zymogen granules. Immersion in formalin for 36 h at room temperature was the optimal fixation condition. Here we designate the procedure as the "eosin-shadow method" and propose that this technique is convenient and useful to help investigators identify zymogen granules more easily in routine pathological examination and histological studies.