What is a Hemangioma?
A hemangioma is a specific type of benign growth composed of an abnormal cluster of blood vessel cells. It forms when endothelial cells, which constitute the lining of blood vessels, proliferate excessively in one location, creating a dense, tangled mass. Although these vascular growths can technically develop on internal organs like the liver, they are most frequently identified as skin lesions in infants, typically appearing within the first few weeks after birth.
Hemangiomas are generally classified based on their location within the skin’s layers. A superficial hemangioma, often referred to as a “strawberry mark,” sits on the skin’s surface as a bright, red, raised lesion. In contrast, a deep hemangioma develops in the underlying layers, presenting as a bluish or skin-colored swelling with a less distinct border. A compound hemangioma exhibits features of both, with a superficial red component overlying a deeper bluish mass.
A defining characteristic of most infantile hemangiomas is their predictable life cycle. They typically undergo a period of rapid expansion during the first few months of life, followed by a stabilization phase, and then a prolonged period of slow, natural regression (involution) over several years.
Causes:- Placental Cell Origin: A prominent theory suggests that hemangiomas may arise from placental cells that migrate and implant within the developing skin of the fetus. These misplaced cells, which share biological markers with placental tissue, are then believed to proliferate abnormally after birth.
- Localized Hypoxia: Another hypothesis proposes that a temporary state of low oxygen (hypoxia) in a small patch of fetal tissue may be the trigger. This oxygen deficit is thought to activate certain genetic pathways that command blood vessel cells to multiply rapidly in a misguided attempt to improve blood supply to the area.
- Hormonal Influence: The fact that hemangiomas are significantly more common in female infants points to a potential role for hormones. It is theorized that estrogen may promote the growth and proliferation of the endothelial cells that form these vascular growths.
- Somatic Mutations: While not typically passed down through families, some hemangiomas may be caused by a somatic mutation. This is a genetic change that occurs by chance in a single cell after conception, which then directs that cell and all its descendants to grow into a vascular mass.
- Female Gender: For reasons that are still being investigated, female infants are diagnosed with hemangiomas at a rate that is three to five times higher than that of male infants, making gender the most pronounced risk factor.
- Low Birth Weight: A baby's weight at birth is a significant predictor. Infants born with a lower-than-average weight, particularly those weighing less than 2.2 pounds (1 kg), have a substantially increased chance of developing one or more hemangiomas.
- Premature Birth: Infants born before their full term are more susceptible. The risk increases with the degree of prematurity, meaning babies born earlier in the gestational period are more likely to have these vascular growths.
- Caucasian Ancestry: There is a clear demographic link related to ethnicity. Infants of Caucasian descent have a higher reported incidence of developing hemangiomas when compared to infants from other racial backgrounds, such as those of African or Asian ancestry.
- Multiple Gestation Pregnancies: Being part of a twin, triplet, or other multiple birth is also associated with an elevated risk. This may be linked to shared placental factors or the lower average birth weights common in these pregnancies.
