Abstract
A 76-year-old woman with dermatomyositis was being treated with prednisolone, tacrolimus, and mycophenolate mofetil. There was a solitary lung nodule in the right middle lobe on chest computed tomography at a routine follow-up examination. A transbronchial lung biopsy was performed, and the histopathologic findings indicated diffuse large B-cell lymphoma. An immunodeficiency-associated lymphoproliferative disorder was suspected, and mycophenolate mofetil was stopped without adding any other therapy. Nine months later, the pulmonary nodule had disappeared on chest computed tomography.