Immunoglobulin G4-related paratesticular fibrous pseudotumor and retroperitoneal fibrosis: a case report.

A 46-year-old man with a past history of retroperitoneal fibrosis was admitted with an enlarged, hard right testis. The paratesticular lesion showed heterogeneous hypoechogenicity on ultrasonography, low signal intensity on T1- and T2-weighted magnetic resonance imaging (MRI), and lack of diffusion restriction on diffusion-weighted MRI. Following steroid treatment, the paratesticular mass was decreased in size on follow-up computed tomography. The radiologic and clinical features are recognized as a manifestation of immunoglobulin G4-related sclerosing disease involving the paratesticular region and retroperitoneum.