A hemangioma is an abnormal proliferation of blood vessels that may occur in any vascularized tissue including skin, subcutaneous tissue, viscera, muscle, synovium, and bone, but they do not spread to avascular tissue such as cartilage. Some believe that hemangiomas are neoplasms while others consider them hamartomas. Abnormal angiogenesis involving cytokines, such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) is suspected. They most often occur in the skin or subcutaneous tissues. Visceral hemangiomas are much less common but may result in organ dysfunction. They also occur in deep soft tissues and bones. Other diseases are associated with hemangiomas. Gorham disease is a process of massive osteolysis, which is believed to be within the spectrum of hemangiomatous disease. Hemangiomas occurring with multiple enchondromas exist in Maffucci syndrome.

Skeletal muscle is the most common site for hemangioma of the deep soft tissue. Intramuscular hemangiomas are often asymptomatic or painless and found as an incidental finding. They may become symptomatic causing pain and swelling. Intramuscular hemangiomas are most commonly found in young people, virtually equal in males and females. The most common location is the thigh. The symptoms of pain and swelling due to increased blood flow through the hemangioma are often exacerbated by exercise, which results in vascular dilation. Rarely, large intramuscular hemangiomas may be associated with significant shunting of blood flow even leading to heart murmurs and/or congestive heart failure similar to that of an arteriovenous fistula.

Imaging: Plain film radiography of soft tissue hemangiomas may demonstrate soft tissue density without or with phleboliths. They may cause benign-appearing periosteal reaction or chronic cortical thickening and remodeling in adjacent bone. Cortical changes may include erosions, thickening, tunneling, and osteopenia. Phleboliths within the soft tissue mass are diagnostic but uncommon. MRI is the imaging modality of choice in concert with plain films. Hemangiomas show increased signal on both T1 and T2 weighted images, frequently with areas of signal void, which may represent fibrous tissue, phleboliths, thrombi or high flow. These signal characteristics with a serpentine pattern of vessels and interspersed fat are diagnostic. Gadolinium enhancement is also noted. Features separating hemangiomas from malignant soft tissue tumors include frequency of lobulation, septation, and central low-intensity dots on T2-weighted images. Hemangiomas tend to enhance markedly compared with malignant soft-tissue tumors. Angiography demonstrates a highly vascular lesion with parallel oriented vessels.

Treatment: The natural course of intramuscular hemangiomas is usually fatty replacement with gradual involution. Therefore, conservative observation is appropriate if symptoms are absent or mild. If symptoms dictate treatment, embolization may be used to provide symptomatic relief of intramuscular hemangiomas. When surgical excision is required, embolization may be used preoperatively to decrease blood loss and recurrence. Excision can provide permanent relief. However, it is usually restricted to hemangiomas contained within a single muscle. If complete resection is not possible they nearly always recur. Radiation has been used as a non-surgical therapy. Chemotherapy has been used for extensive hemangiomatosis. Steroids have been used for some of the syndromic versions.