IgG4-related inflammatory pseudotumour of the gallbladder in acute cholecystitis

Immunoglobulin G4 related pseudotumour (IgG4-PT) of the gallbladder is a very rare condition formed by the infiltration of IgG4-positive lymphocytes and plasma cells, resulting in a mass effect that can mimic malignancy. We present a case of a patient who underwent an unremarkable laparoscopic cholecystectomy for symptoms of early cholecystitis that was incidentally found to have an inflammatory tumour adjacent to the cystic duct. Identification remains difficult and histopathology remains a cornerstone in correct diagnosis. Histopathological confirmation is based on meeting two of three histological criteria in the correct clinical context. IgG4-PT is a rare cause of cholecystitis and requires ongoing surveillance for IgG4 cholangiopathy.