Unusual soft tissue infiltrates with 18F-FDG uptake in a patient with hairy cell leukemia.

Hairy cell leukemia (HCL) is an uncommon B-cell lymphoproliferative disorder, representing approximately 2% of leukemias. Diagnostic features include pancytopenia, splenomegaly, bone marrow reticulin fibrosis, and circulating hairy cells. Less commonly, there may be involvement of the liver and lymph nodes. We present a case of a 53-year-old man with HCL who was found to have soft tissue masses within the mediastinum and neck during pretreatment workup. An F-FDG PET/CT scan was requested to assess these lesions before treatment. These extensive infiltrates were FDG avid, and core biopsy of the mediastinal tissue was undertaken. Results were consistent with HCL.