IgG4-related Disease: A Mass Lesion in the Intrarenal Sinus near the Renal Pelvis.

A 52-year-old Japanese woman was admitted to our hospital with the renal pelvic mass lesion detected on a health screening examination. The surgical specimen contained a mass exhibiting the histological features of immunoglobulin (Ig)G4-related disease, including lymphoplasmacytic infiltration and sclerosis with numerous IgG4-producing plasma cells. Postoperatively, an elevation of the serum IgG4 level was confirmed at 403 mg/dL; however, there was no evidence of tubulointerstitial nephritis or glomerulopathy, including membranous nephropathy, and the urothelium of the renal pelvis was intact without inflammation. We herein report this case in which IgG4-related disease of the renal pelvic region presented with a mass lesion in the intrarenal sinus near the renal pelvis, not 'pyelitis' (as described by Stone).