Rare case of IgG4-related retroperitoneal fibrosis mimicking renal cell carcinoma: A diagnostic challenge.

IgG4-RD is an immune-mediated systemic fibroinflammatory condition with characteristic clinicopathological findings. The exact etiology is uncertain. A combination of environmental and genetic factors is considered to be involved. It can affect multiple organs often mimicking malignancy or infectious disorder. Because of myriad of clinical presentations, the clinical diagnosis is cumbersome and requires a detailed histopathological, radiological, and serological workup. IgG4-retroperitoneal fibrosis is usually seen as a component of systemic manifestation of the disease that presents as mass lesion causing pressure and pain symptoms. These clinical symptoms are usually of insidious onset with gradually progressive course. The early diagnosis and treatment is essential to prevent its long-term irreversible complications. Isolated retroperitoneal fibrosis due to IgG4-RD is rare, as is being reported in our elderly male patient. Our case report highlights the rare presentation of IgG4-related RPF mimicking renal cell carcinoma.