Lymphoplasmacytic lymphoma relapse presenting as isolated multifocal subcutaneous adipose tissue infiltrates on 18F-FDG PET/CT.

Lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinemia (WM) is an uncommon mature B cell lymphoma usually involving the bone marrow and, less commonly, the spleen and/or lymph nodes. This case presents a pathology-confirmed isolated extramedullary relapse of LPL, located in subcutaneous adipose tissue, 5 years after successful treatment of WM.