Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare disorder characterized by the infiltration of clonal CD8+ T-cells into subcutaneous adipose tissue. Most patients present with indurated plaques on the trunk or extremities accompanied by the gradual onset of constitutional symptoms. Hemophagocytic lymphohistiocytosis (HLH) occurs in about one third of patients, and recent genetic data implicate germline mutations in Hepatitis A-virus Cellular Receptor 2 (HAVCR2) as causative of SPTCL in a subset of patients prone to this complication. Radiographic extension beyond the subcutaneous adipose tissue is rare, with the largest multi-institutional review of SPTCL to date referencing only a few isolated cases with PET avid lesions in the peri-renal, peri-cardiac, and perinodal fat pads.  In this report, we present the case of a 35 year-old female who, over the course of 2 months, developed a slow growing indurated plaque on the left thigh along with clinical and laboratory signs of HLH. PET scan revealed scintigraphic findings suggestive of peritoneal carcinomatosis of unclear primary and a markedly elevated CA 125 level worrisome for ovarian cancer. Subsequent biopsy of the involved omental tissue and skin revealed identical histopathologic features diagnostic of SPTCL.  Cyclosporine dosed at 4 mg/kg/day was initiated with marked relief in clinical symptoms and resolution of laboratory abnormalities over a six week period. To our knowledge, this is the 6th biopsy-proven case of omental/mesenteric involvement of SPTCL and the first to be successfully treated with an immunosuppressant.