Hemosiderotic fibrolipomatous tumor (HFLT) is a slow-growing subcutaneous mass composed of hemosiderin pigment, spindle cells, and mature adipocytes. HFLTs usually present in the fifth to sixth decades of life, with a median age of onset of 50 years, and is more frequent in females, at a ratio of 2.8:1. Fewer than 100 cases have been reported.

HFLT appears most commonly as a variably circumscribed, green-blue to brown plaque on the dorsal aspect of the foot or ankle. More rarely, HFLTs have been reported on the hands, wrists, forearms, legs, and face. Plaque size ranges from 0.1-19 cm in reported cases (average size around 7.7 cm). The lesions may be soft, mobile, and tender. To date, only 1 case has been reported of HFLT arising within bone.

HFLT was originally thought to arise as a reactive inflammatory process as, rarely, patients with HFLT have reported a history of trauma and/or vasculopathy at the site of the tumor. Therefore, it has been postulated that repeated minor blood vessel damage in tight dorsal compartments of highly mobile joints may be a factor in the development of HFLT.

However, 17 reported cases have shown chromosomal translocation of (1;10)(p22;q24) and/or rearrangements in TGFBR3/MGEA5 with cytogenetic analysis; therefore, a neoplastic origin is also posited. Cases of HFLT have also been reported to progress to a hybrid of HFLT and myxoinflammatory fibroblastic sarcoma (HFLT-MIFS), and these cases also display this chromosomal rearrangement.

HFLT displays a relatively high recurrence rate after surgical resection of 30%-50%. A single case of transformation into a low-grade unclassified pleomorphic sarcoma has been reported.