Immunoglobulin G4-related cholecystitis mimicking a locally advanced gallbladder cancer-a case report and review of literature.

Immunoglobulin G4 (IgG4)-related disease is a multi-organ immune-mediated condition that can mimic many inflammatory, malignant, and infectious disorders. Isolated IgG4-related cholecystitis without systemic manifestation is extremely rare. We report a rare case of IgG4-related disease with its clinical, radiological and histopathological findings involving only the gallbladder which presented initially as unresectable locally advanced gallbladder cancer on imaging but was diagnosed as IgG4-related cholecystitis preoperatively depending upon serum IgG4 levels and immunohistochemistry. Patient was successfully treated with steroids followed by simple cholecystectomy in view of symptomatic gallstones. Preoperative diagnosis is challenging for IgG4-related cholecystitis in view of mass like appearance of the lesion with surrounding invasion on imaging so most of the cases are reported postoperatively. Knowledge of this disease as differential for malignancy can save patients from extensive resections in view of its steroid responsive nature. Xanthogranulomatous cholecystitis mimicking gallbladder cancer can coexist with this disease.