Case Report: Membranous fat necrosis of the gallbladder as the cause of peculiar foreign body reaction in a patient with severe chronic cholecystitis

Membranous fat necrosis (MFN) in the gallbladder is rare. We found marked MFN as the cause of peculiar foreign body reaction in a Japanese woman in her late seventies, with severe chronic cholecystitis. Histopathological examination of the extirpated gallbladder revealed severe grade chronic cholecystitis accompanied by many multinucleated giant cells and phagocytizing yellowish wavy membranous substance in the subserosal layer. The results of Sudan black B, Luxol fast blue, and Ziehl-Neelsen staining of the substance were all positive. CD68 antibody was strongly positive in multinucleated giant cells. These findings suggested that the membranous structures were the products of MFN, which was recognized as a foreign body and phagocytized by macrophages. Stenosis of intramural sclerotic arteries induced chronic circulatory disturbances leading to MFN that resulted in a peculiar foreign body reaction in the subserosal fatty tissues of the gallbladder. To our best knowledge, these findings have not been reported in the literature thus far.