Slowly Expanding 18 F-FDG PET-Positive Irregular Opacities in the Lung Due to Diffuse Lymphoid Hyperplasia Preceding Rheumatoid Arthritis.

Pulmonary diffuse lymphoid hyperplasia (DLH), a nonneoplastic lymphoproliferative disorder (LPD), is extremely rare, and no PET/CT findings have been reported for pulmonary DLH. We observed slowly expanding irregular opacities with 18 F-FDG accumulation (SUV max , 3.64) in the right lower lobe of a 51-year-old asymptomatic man. The patient underwent video-assisted thoracoscopic biopsy on suspicion of malignant lesions. Histologically, no neoplastic cells were present, and the lesion was consistent with DLH. Six months later, the patient developed rheumatoid arthritis. DLH should be considered in the differentiation of PET-positive irregular opacities, even in the absence of known immune abnormalities.