Immunoglobulin G4-Related Disease Mimicking an Anterior Mediastinal Tumor.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated collection of disorders that were once thought to be unrelated but are increasingly being recognized as a single entity. The tumor-like swelling of the involved organ, a storiform pattern of fibrosis, and a serologic elevation of IgG4 can lead to the diagnosis of IgG4-RD. The usual organs affected are the pancreas, biliary tract, and salivary and lacrimal glands. There have been few reports of intrathoracic cases, which usually have pulmonary lesions. We here report a case of IgG4-RD of the anterior mediastinum in the form of a mass, a rare entity, the second such patient described in the literature to date.