A mesenchymal neoplasm characterized by solitary or multiple nodules involving the skin, striated muscles, bones and, sometimes, viscera. It usually appears as a subcutaneous nodule, but can also appear as an ulcer, pedunculated lesion, or similar to a hemangioma. Histology shows well-circumscribed tapered cell lobes, resembling smooth muscle cells. At its center, perivascular round cells (hemangiopericitoides) are usually observed, giving a biphasic appearance.