Hemangioma is a benign tumor that occurs in the endothelial lining of the blood vessels. These tumors usually develop within the first few weeks of life but often resolve independently by time a child is ten years of age. Hemangioma is the most common type of tumor found in children.

The term hemangioma was first used by Mulliken and colleagues, but originally referred to any tumor like structure occurring in the vessels, regardless of whether it was present at birth, developed soon after birth or developed late in life. Mulliken categorised these tumors into the following groups:

• Tumors that were self-involuting, meaning they shrunk by themselves
• Tumors that grow but did eventually disappear
• Tumors that are present at birth and cause permanent abnormality

This classification helped to differentiate between tumors that would resolve independently without requiring treatment and those that would be permanent. Examples of permanent lesions include port-wine stains and swollen veins.

Stages of development in hemangioma

There are essentially three stages of hemangioma development and these include:

• The proliferation stage, where the hemangioma grows rapidly. This stage can last as long as one year.
• The resting stage, where very little change occurs in the lesion’s appearance. This stage lasts until the child is aged around one to two years.
• The involution stage, where the tumor starts to shrink. In 50% of cases, the tumor has disappeared by the time the child reaches five years of age and most cases have  disappeared by time children are ten years old.
• In a few rare cases, hemangiomas do no diminish in size or disappear.

Pathology

The endothelial cells lining the blood vessels multiply at an abnormally fast rate and eventually form a lump. Hemangiomas may be superficial and develop on the surface of the skin or they may be deep and form below the skin surface.

Surface hemangiomas may be warm to the touch, as they are supplied by their own blood vessels. Their texture may also resemble the surface of a strawberry and these lesions are sometimes referred to as strawberry hemangiomas. Hemangiomas can also be a combination of superficial and deep, appearing as a raised red area with a bluish swelling caused by blood vessels deeper down in the skin.