Melanocytic nevi, commonly known as moles, are benign growths on the skin formed by clusters of pigment-producing cells called melanocytes. These spots are extremely common, and babies can have moles either present at birth or developing shortly thereafter. While moles in infants are generally non-threatening, their presence requires observation to ensure they follow a normal pattern of growth. Understanding the different types of moles is important for effective monitoring.
Moles Present at Birth
A mole visible at birth or appearing within the first year is classified as a Congenital Melanocytic Nevus (CMN). These occur in approximately 1% of newborns, resulting from a localized overgrowth of melanocytes during fetal development. CMN often appear as light to dark brown patches or plaques, which may be slightly raised or have an irregular surface texture. Coarse, dark hair within the mole, known as hypertrichosis, is also a common characteristic.
The size of a CMN determines the level of long-term monitoring required. Physicians classify these based on their projected adult diameter: small (less than 1.5 cm), medium (1.5 cm to 20 cm), and large or giant (greater than 20 cm). Large or giant congenital nevi carry an elevated lifetime risk of developing melanoma, estimated to be between 5% and 10%. Small and medium-sized CMN have a low risk of malignant transformation, comparable to the general population’s risk.
Any CMN requires consistent evaluation by a pediatrician or dermatologist starting in infancy. These moles tend to grow proportionally with the child, and some may become lighter over time. Close photographic documentation and regular measurements are standard practice for tracking the CMN’s appearance and growth pattern.
Moles That Appear After Infancy
Moles that develop after the first year of life are considered acquired nevi. The development of new spots during early childhood is a normal process, typically beginning around two to three years of age. Their number continues to increase throughout childhood and adolescence, often peaking in the third decade of life.
These common moles are usually small, less than 6 millimeters in diameter, and exhibit a uniform color ranging from tan to dark brown. They are generally round or oval with smooth, well-defined borders. Acquired moles are influenced by genetic predisposition and environmental factors, particularly sun exposure.
It is normal for a child to develop dozens of these small, uniform moles as they grow. As a child matures, these moles may naturally change, sometimes becoming more raised or fading in color. Benign acquired nevi tend to look similar to each other, maintaining a consistent pattern across the skin.
Warning Signs Requiring Pediatric Consultation
Parents should remain vigilant for specific changes that warrant consultation with a pediatrician or dermatologist. The standard ABCDE criteria, typically used for adults, are adapted in a pediatric context because melanoma in children can present differently. The most important factor to monitor is Evolution, meaning any significant change in a mole’s appearance over a short period, such as rapid growth, shape changes, or darkening color.
The ABCDE criteria include:
- Asymmetry: One half of the mole does not match the other half when an imaginary line is drawn through the center.
- Border: An irregular or blurred border should raise concern; healthy moles usually have smooth, distinct edges.
- Color: The mole should be uniform, but multiple colors—such as shades of brown, black, white, red, or blue—can signal an issue. Pediatric melanomas can sometimes appear uniform, making rapid change more relevant than color variation.
- Diameter: While the adult criterion flags moles larger than 6 millimeters, smaller moles can also be concerning if they exhibit other atypical features.
Beyond the ABCDEs, specific features associated with atypical growths in children include the EFG signs: Elevated, Firm, and Growing consistently for a month or more. A mole that becomes noticeably raised, feels hard to the touch, or continues to rapidly increase in size needs prompt medical attention. Other red flags include persistent itching, bleeding, crusting, or the development of a non-healing sore on or near the mole.