Postchemotherapy Histiocyte-Rich Pseudotumor of the Spleen Simulating Residual Disease in a Patient With Non-Hodgkin Lymphoma on FDG PET/CT.

A 64-year-old man was treated with multiagent chemotherapy owing to high-grade non-Hodgkin lymphoma presenting as a bulky disease involving the spleen. Interim and posttreatment sequential FDG PET/CT scans revealed a residual splenic mass showing markedly intense FDG uptake suspected of a residual viable lymphoma. To definitely decide about the appropriate treatment, a laparoscopic splenectomy was performed. Histopathologic specimen was compatible with the rare diagnosis of postchemotherapy histiocyte-rich pseudotumor of the spleen, a potential pitfall simulating viable disease on FDG PET/CT.