18F-FDG PET/CT for Staging and Evaluation of Therapy in a Patient With Unusual Hairy Cell Leukemia Presentation.

Hairy cell leukemia is a rare hematologic malignancy characterized by splenomegaly, pancytopenia, and susceptibility to infections. We report a case of a 66-year-old man, diagnosed with hairy cell leukemia, without severe cytopenias and splenomegaly, but with an extensive pathological retroperitoneal mass and infiltration of the spleen and skeletal involvement. All findings were highly avid on pretreatment F-FDG PET/CT scan. Treatment response evaluation F-FDG PET/CT scan showed normalization of FDG uptake on all previously pathological sites.