Primary pulmonary diffuse large B-cell lymphoma presenting multiple nodules mimicking metastasis: A case report.

Primary pulmonary diffuse large B-cell lymphoma is a rare entity. We describe a case of pulmonary lymphoma with multiple nodules mimicking metastases in a treated patient with rheumatoid arthritis. A 73-year-old man was diagnosed with rheumatoid arthritis at the age of 30. He was treated with leflunomide. He was followed up for a nontuberculous mycobacterial infection. He underwent percutaneous coronary intervention for acute myocardial infarction at the age of 70. In April 2022, routine follow-up revealed new-onset multiple nodules on chest computed tomography (CT). A position emission tomography/CT scan with 18F-fluorodeoxyglucose showed a low-high maximum standardized uptake value by multiple nodules. Pathologic examination of a video-assisted thoracic surgical biopsy revealed pulmonary diffuse large B-cell lymphoma. Systemic chemotherapy with rituximab, cyclophosphamide, vincristine, and prednisolone reduced and eliminated multiple nodules. Pulmonary lymphoma should be considered as a differential diagnosis in the case of multiple nodules on a chest CT.