F-18 FDG PET/CT detecting thyroid plasmacytoma after the successful treatment of gastric large B-cell lymphoma.

摘要

Thyroid plasmacytoma is a rare form of extramedullary plasma-cytoma. We describe an 82-year-old man with gastric large B-cell lymphoma who had complete response after receiving chemotherapy and rituximab, an anti-CD20 chimeric monoclonal antibody. Thyroid uptake was seen on follow-up F-18 fluorodeoxyglucose-positron emission tomography/computerized tomography scan (FDG PET/CT) imaging. The left thyroid lobe uptake proved to be plasmacytic neoplasm, whereas the right lobe uptake represented thyroiditis. FDG PET scan is a useful tool for monitoring disease activity in lymphoma patients; however, other benign processes could lead to false positive findings.