IgG4-related inflammatory pseudotumor of the kidney mimicking renal cell carcinoma: A case report.

IgG4-related disease is a recently recognized clinical entity. It is characterized by diffuse organ swelling or mass formation, a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells with fibrosis and typically an increased serum IgG4 concentration, which may affect various organs. An 80-year-old woman with an otherwise unremarkable previous medical history was revealed to have a renal mass that was indicative of renal malignant carcinoma, for which a radical nephrectomy was performed. The mass was diagnosed as an IgG4-related inflammatory pseudotumor, which was histopathologically confirmed. The patient is currently well without evidence of IgG4-related disease at 3 months post-surgery, and did not require any additional therapy.