Epidemiology
It is one of the commonest benign vascular lesions of the soft tissues. It is usually noticed in childhood or in young adults and, when it is deep, it appears most often within the muscles of the thigh and the leg. In everyday speech "hemangioma" is used for almost any vascular-looking mark or lump, so the name on its own does not yet tell you which lesion is involved.
Basic features
It presents as a soft swelling, sometimes slightly bluish if it is superficial, which may ache with exercise or swell when the limb is left hanging down. Radiographs may show phleboliths —small round calcifications within the vessels— and MRI usually shows serpiginous vessels interspersed with fat. The important distinction is not between "benign and malignant", but between a hemangioma (a proliferation of vessels, that is, a benign tumor) and a vascular malformation (a developmental defect of the vessels): they look very similar, are easily confused, and the treatment is different.
Usual treatment
Many asymptomatic lesions are simply monitored. When they cause trouble, the starting point is conservative measures (compression, pain relief, adjusting activity). In low-flow lesions sclerotherapy may be considered, and surgery is reserved for well-localized, symptomatic lesions, bearing in mind that an intramuscular hemangioma can infiltrate between the muscle fibers and does not always have a clean edge that allows it to be removed completely. As with any vascular anomaly, the decision is made by an experienced team.
Outcomes and prognosis
It is a benign lesion: it does not metastasize and it does not turn into a sarcoma. Symptoms are usually well controlled, although intramuscular lesions that cannot be removed completely may become bothersome again over time and require stepwise management.