Figure 2 Chronic cholecystitis with mucosal hyperplasia, cholesterolosis, and Actinomyces spp. sulfur granules. The gallbladder exhibits varying degrees of mucosal hyperplasia and transmural fibrosis (A, B). On this images, (1) cholesterolosis is noted as aggregates of xanthomatous histiocytes in the sub-epithelial position (white arrows, B, C); (2) Rokitansky-Aschoff sinuses, small invaginations in the gallbladder wall into the muscular layer, can be observed (black asterisks, A, B); (3) sulfur granules are visible on the hematoxylin and eosin (HE) stain (black arrows, A–D); and (4) gram-positive filamentous bacteria (bacilli) compatible with Actinomyces spp. are visible on Gram-stained specimens (red arrows, E). Panels A–D represent the cholecystectomy specimens stained with HE (40× in A, E, 100× in B, and 400× in C). Panels B, C are sequential views of the same structure at increasing magnification (black squares in A, B). Panel E represents the cholecystectomy specimens stained with the Gram method (Gram 100× magnification).