Three different CT and FGD PET/CT findings of pulmonary involvement in methotrexate-associated lymphoproliferative disease.

Lymphoproliferative disease (LPD) is one of the complications of methotrexate (MTX) therapy. In MTX-associated LPD (MTX-LPD), LPD lesions limited to the lungs are rare and show various types of opacity. A 75-year-old woman with rheumatoid arthritis (RA) presented with myalgia. She had been taking MTX for 11 years. Chest computed tomography (CT) scans showed a nodule in the left lower lobe that had grown significantly and a new nodule in the right lower lobe. 18F-fluorodeoxyglucose (FDG)/positron emission tomography (PET)/CT revealed significant FDG uptake in these nodules. Transbronchial biopsy specimen showed diffusely distributed CD20-positive lymphoid cells, and we made a diagnosis of MTX-LPD. All lung lesions disappeared within months after the immediate discontinuation of MTX. We also had two other patients with MTX-LPD lung lesions that had high FDG uptake. FDG PET/CT might be a useful diagnostic tool as it may reflect disease progression and help identify separate lesions.