:PHAT (pleomorphic hyalinizing angiectatic tumor) is a rare, locally aggressive, low-grade mesenchymal neoplasm of uncertain lineage with a predilection for the lower extremities. We report a 74-year-old woman with an enlarging mass on the right popliteal fossa undergoing FDG PET/CT to characterize its biological activity. Increased accumulation of FDG (SUVmax, 23.0) in the solid component of the tumor was seen. Diagnosis of PHAT was confirmed by examination of the surgical resection specimens. This case showed significant FDG accumulation relative to its pathological low-grade malignant nature.