A case of IgG4-related disease associated with diffuse large B cell lymphoma.

In June 2008, a 74-year-old male was diagnosed with IgG4-related disease including histologically proven IgG4-related prostatitis, and then followed as an outpatient. In July 2011, cervical, chest, and abdominal computed tomography (CT) revealed right parotid gland swelling and lymph node enlargement of the supraclavicular, mediastinal, left hilar, porta hepatis, and para-aorta. A biopsy of the right parotid gland was performed, and we diagnosed diffuse large B-cell lymphoma (DLBCL). As malignancies are possible complications for patients with IgG4-related disease, we must be careful in the follow-up of IgG4-related disease patients.