Fluorine-18-fluorodeoxyglucose uptake in rheumatoid arthritis-associated lung disease in a patient with thyroid cancer.

An 18F-fluorodeoxyglucose (FDG) whole-body PET scan was performed on a thyroid cancer patient with long-standing rheumatoid arthritis who presented with pulmonary nodules. A recent diagnostic radioiodine whole-body scan was negative. However, the 18F-FDG scan demonstrated intense uptake in the chest lesions as well as in several joints affected by rheumatoid arthritis. Fine-needle aspiration of a pulmonary nodule revealed inflammatory reaction and absence of malignant cells, fungus and tuberculous infection. A repeat chest CT scan after 7 mo of steroid therapy showed a marked decrease in the size and number of nodules. In thyroid cancer patients, 18F-FDG uptake in the lung may not necessarily represent pulmonary metastases. This case illustrates a benign, unrelated pathology namely, rheumatoid arthritis-associated lung disease.