Soft-tissue angiomatosis in adulthood: a case in the forearm showing a prominent myxoid adipose tissue component mimicking liposarcoma.

Soft-tissue angiomatosis is a rare condition characterized by diffuse proliferation of benign vascular structures, accompanied by mature adipose tissue, which affect a large segment of the body in a contiguous fashion. Most patients present in childhood or adolescence. We report a case of large soft-tissue angiomatosis, located in the left forearm of a 65-year-old man, which showed extensive intramuscular and intermuscular infiltration, and embracement of the radius and the main vascular and neural bundles of the forearm. Due to the deep location, large size, ill-defined limits and non-homogeneous composition with areas suggestive of an adipose component in the radiological examination, the lesion raised the possibility clinically of a liposarcoma. The myxoid adipose tissue component of the lesion, a feature previously undescribed, and the predominance of small, capillary-sized vessels were considered concordant with the clinical diagnosis. This presentation is rare. The features of the lesion made complete surgical excision impossible and amputation of the extremity was considered the best treatment. The main differential diagnoses include infiltrating lipoma, myxolipoma, angiomyxolipoma, angiolipoma, intramuscular angioma, liposarcoma and low-grade myxofibrosarcoma. In conclusion, angiomatosis might simulate liposarcoma, particularly if the mass is large, heterogeneous, myxoid and appears later in life.