Unique case of IgG4-related disease of the renal pelvis involving the inferior vena cava masquerading as locally advanced urothelial cancer

Immunoglobulin G4-related disease (IgG4-RD) is a systemic disease which can affect any organ or tissue in the body but most commonly affects the pancreas, biliary ducts, salivary glands, ocular system and lymph nodes; renal involvement is relatively uncommon and there are no previous reported cases of inferior vena cava involvement. Herein, a 48-year-old Asian man with an unremarkable medical history was found to have an obstructing right renal pelvis mass extending to and involving the inferior vena cava, highly suspicious for upper tract urothelial carcinoma that could not be ruled out based on ureteroscopy and urine cytology. Open radical nephroureterectomy with enbloc resection of a segment of the inferior vena cava and left renal vein ostium was performed, with reconstruction of the inferior vena cava and left renal vein with polytetrafluoroethylene grafts. Final histopathology confirmed the diagnosis of IgG4-related disease. This case demonstrates that IgG4-related disease can mimic upper tract urothelial cancer and should be considered as a diagnosis in atypical presentations of tumours of the upper urinary tract.