Birthmarks (Skin Nevi)
Skin nevi are common skin tumors caused by abnormal overgrowth of cells from the epidermal and dermal layers of the skin. Most nevi are benign, but some precancerous types must be monitored or removed. Types of nevi found in children include:
- Congenital melanocytic nevi
- Giant congenital melanocytic nevi
- Blue nevi
- Epidermal nevi
- Sebaceous nevi
- Spitz nevi
The giant congenital nevus is greater than 10 cm in size, pigmented and often hairy. Between 4 and 6 percent of these lesions will develop into a malignant melanoma. Since approximately 50 percent of the melanomas develop by age 2 years and 80 percent by age 7 years, early removal is recommended.
Although removal of giant lesions can be quite challenging, the advances in surgical techniques and pediatric anaesthesia available in children’s hospitals has greatly improved the safety of treatment.
Congenital melanocytic nevi are found in about 1 percent of newborns. These small nevi are visible at birth and are deeper and larger than nevi acquired later in life. Over 90 percent are less than 4 cm in size, and only 1 percent are large enough to be a giant congenital nevus. Unlike the giant form, the risk of malignancy in these small nevi appears to be greatest at or after puberty, thus allowing more time for consideration of treatment.
A blue nevus is a blue-black nodule with a smooth surface that may be present at birth or may not appear until puberty. The deep pigmentation is due to large amounts of melanin pigment within the deeper dermis. The nevus of Ota and Ito are blue nevi with regional localization. Malignant degeneration is rare and these lesions are generally removed for cosmetic reasons.
Epidermal nevi are linear, raised and at times “warty” lesions which may occur on the head. When associated with other congenital disorders, the child may have epidermal nevus syndrome. The risk for malignant degeneration is unknown but uncommon.
The sebaceous nevus is a congenital hamartoma (normal cells outside of their normal locations) of the sebaceous glands. By adolescence these lesions often thicken and run a risk of malignant degeneration, which is why removal is recommended.
Spitz nevi are firm and pink and may be confused with a small vascular lesion. These lesions recur if not completely removed. It is unknown whether this lesion is a precursor to malignancy.
Treatment for small lesions is simple excision and closure, sometimes performed by a pediatric dermatologist. For larger lesions, movement of skin flaps or tissue expansion may be needed. The pediatric craniofacial plastic surgeons are members of the vascular lesion team and provide assurance that complex excisions and reconstructions will yield an optimal cosmetic and functional outcome.
Rady Children’s Vascular Lesion and Birthmark Clinic also treats skin nevi, as well as vascular birthmarks, using a multidisciplinary approach.