A hemangioma is a benign growth made up of an abnormally dense collection of blood vessels.
Often referred to as a birthmark, these tumors usually develop on the face, neck, scalp or back shortly after birth. They usually present as a rubbery, red or purple mass, although they can vary significantly in size, color and shape. These growths are sometimes also referred to as strawberry marks.
An infant is usually only born with one hemangioma, but more may be present, particularly if the child is from a multiple birth. Hemangiomas are not inherited but several members of the same family may have the lesions, simply because they are so common.
A hemangioma usually grows rapidly and starts to form a protruding spongy mass during the first year of life. Following this, the growth gradually starts to resolve and almost half of all hemangiomas have disappeared by time children reach the age of five. Children who developed a hemangioma in childhood often have no trace of the growth by time they reach 10 years of age.
Most hemangiomas develop on the surface of the skin, but they can also affect deeper skin layers and grow underneath the skin.Hemangiomas usually appear at around two weeks after birth, although deep hemangiomas may not be visible until four months of age.
The cause of hemangiomas has not yet been established, but these growths are more common among females, babies born prematurely and white infants.
Although it is not understood exactly what causes a hemangioma to develop, the different types of tumor are linked to different causes. For example, abnormal vascular development in the developing embryo is associated with infantile hemangiomas, although what causes the abnormality cannot be established.
Similarly, a hemangioma may occur as the result of injury but whether or not an injury can actually cause one of these growths to develop has not yet been confirmed.
Hemangiomas can also develop during pregnancy but resolve once the child is born, while others are associated with genetic conditions.
No profession involving exposure to certain chemicals or radiation, for example, has so far been linked to the development of hemangiomas and neither has any particular medication, food or activity during pregnancy.
However, researchers have suggested several theories to explain how these growths arise.
Some experts believe that estrogen signalling may be an important factor in the proliferation of hemangioma and in 2007, researchers suggested that hypoxia of localized soft tissue combined with increased estrogen levels after birth may stimulate the formation of hemangioma.
Another theory proposed by researchers from Harvard and the University of Arkansas is that the placenta embolizes to the fetal dermis at some point during gestation, which causes a hemangioma to form.
However, further research form Duke University contradicted this hypothesis and research into the cause of hemangioma growth is still ongoing.
A hemangioma does not usually require treatment because these growths do not become cancerous.
However, the tumor may need to be removed if it is causing difficulty with vision, eating or breathing, for example. Some growths can also be disfiguring and people may seek advice regarding their removal for cosmetic reasons.