Immunoglobulin G4-Related Disease Association With an Isolated Anterior Mediastinal Tumor.

We treated a patient with immunoglobulin G4-related disease (IgG4-RD) exhibiting an isolated anterior mediastinal mass with high 2-[18F]-fluoro-2-deoxy-D-glucose accumulation, which mimicked thymoma. The 71-year-old man had a 47-mm anterior mediastinal mass shadow and was referred to our department. Because positron emission tomography revealed the mass to have a high level of 2-[18F]-fluoro-2-deoxy-D-glucose accumulation, we diagnosed it as suspected thymoma; thoracoscopic resection of the tumor was then performed. Immunohistologic findings, however, yielded a diagnosis of IgG4-RD. Despite its rarity, IgG4-RD should be borne in mind as a potential diagnosis in case of isolated anterior mediastinal mass shadow.