IgG4-related stomach muscle lesion with a renal pseudotumor and multiple renal rim-like lesions: A rare manifestation of IgG4-related disease.

We describe a 74-year-old man with immunoglobulin G4-related disease (IgG4-RD) presenting with gastric cancer, stomach and kidney lesions. For 15 years, the patient had been treated under a diagnosis of sclerosing cholangitis, which was revealed to be IgG4-RD only when the cancer was found. Histology revealed the gastric cancer and IgG4-related lesion in the muscularis propria to be separate. This case suggests that the stomach muscle can also be a site of involvement of IgG4-RD.