Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a very rare type of cutaneous lymphoma that localizes primarily in the subcutaneous adipose tissue without palpable involvement of the lymph nodes. Most often, it presents as multiple, painless, subcutaneous nodules on the extremities and trunk. In this study, we describe an unusual case of SPTCL that mimicked phlegmonous inflammation; PET/CT revealed massive diffuse involvement of the lower legs, low-grade nodal active disease, and occult involvement of the intra-abdominal visceral fat. A repeat PET/CT study after CHOP chemotherapy revealed complete resolution of abnormal FDG uptake in the initially involved sites.