18F-FDG PET/CT findings in hepatosplenic Gamma-Delta T-cell lymphoma: case reports and review of the literature.

Hepatosplenic Gamma Delta T cell lymphoma (γδHSTL) is a rare, highly aggressive, and rapidly lethal T cell lymphoma which manifests 18F-FDG PET/CT findings that can mimic benign conditions. Patients with γδHSTL present with unexplained symptoms of a hematologic malignancy like the B symptoms of lymphoma including weight loss, fevers, and night sweats, as well as, splenomegaly and hepatomegaly. Thrombocytopenia, anemia, or neutropenia are also common due to spleen, liver and bone marrow involvement. The peripheral blood, however, typically does not show abnormal T cells. The clinical and 18F-FDG PET/CT findings are presented for 3 patients with γδHSTL. Patients with γδHSTL may have a normal 18F-FDG PET/CT or an 18F-FDG PET/CT with any combination of the three findings: splenomegaly with intense FDG uptake; hepatomegaly with increased FDG uptake; and diffuse, increased FDG uptake in the bone marrow. Importantly, lymphadenopathy is usually absent, and most patients show morphologically normal lymph nodes with normal FDG uptake. Due to the aggressive nature of the disease, γδHSTL is a critical diagnosis to consider in patients who present with clinical signs of suspected hematologic malignancy and variable 18F-FDG PET/CT findings. The absence of lymphadenopathy and normal FDG uptake in lymph nodes are typical pertinent negative findings that differentiate γδHSTL from other lymphomas. A bone or liver biopsy is frequently necessary to establish the diagnosis and should be recommended.