Birthmarks are common skin markings that appear at or shortly after birth. While most are harmless, a natural concern arises regarding their potential to become cancerous. The vast majority are benign and pose no threat of cancer. However, some types warrant closer attention due to a small, increased risk of malignant transformation.
Understanding Different Birthmarks
Birthmarks are categorized into two main types: vascular birthmarks and pigmented birthmarks. Vascular birthmarks result from blood vessels that did not form as expected during fetal development. These are often red, pink, or purple, and can be flat or raised.
Examples include hemangiomas, which may appear as bright red, raised “strawberry marks” on the skin’s surface or bluish masses deeper under the skin. Another common type is the port-wine stain, a flat, purplish-red mark made of dilated blood capillaries, often found on the face and typically permanent. Salmon patches, also known as stork bites or angel kisses, are faint red marks that commonly appear on the forehead, eyelids, or neck and usually fade within the first few years of life.
Pigmented birthmarks are formed by clusters of melanocyte cells, responsible for skin color. These vary in color from tan, brown, or black, to bluish-gray. Common examples include moles (pigmented nevi), which are raised or flat growths present at birth (congenital nevi) or developing later. Café-au-lait spots are light brown, oval-shaped patches resembling coffee with milk. Dermal melanocytosis (Mongolian spots) are flat, bluish-gray patches often found on the lower back or buttocks, which tend to fade over time.
Cancer Risk in Specific Birthmarks
While most birthmarks are benign, certain moles, particularly congenital melanocytic nevi (CMN) present at birth, carry a slightly increased risk of developing into melanoma. CMN vary in size, color, and texture. The risk of melanoma within a CMN is generally low, but it increases with the birthmark’s size; larger CMN (over 20 centimeters) have a higher lifetime risk.
The overall incidence of melanoma in CMN is low (1-2%), but for very large CMN (over 40 cm), the lifetime risk can range from 10-15%. Melanoma can develop within the nevus or, with very large lesions, in associated melanocytes in the brain and spinal cord. Most melanomas linked to giant CMN are diagnosed in early childhood. Vascular birthmarks do not carry a risk of becoming cancerous.
Recognizing Concerning Changes
Monitoring pigmented birthmarks for changes is important. Healthcare providers use the “ABCDE” rule to identify potential signs of melanoma:
Asymmetry: One half of the mole does not match the other.
Border: Irregular, ragged, notched, or blurred edges.
Color: Uneven coloration or multiple shades of brown, black, tan, white, red, or blue.
Diameter: Often larger than 6 millimeters, roughly the size of a pencil eraser.
Evolving: Any change in size, shape, color, elevation, or new symptoms like itching or bleeding over time.
Any birthmark that looks different from others on your body (the “ugly duckling” sign) also warrants attention. These signs require professional evaluation.
When to Consult a Professional
It is advisable to seek medical advice for any birthmark or mole that shows new or concerning changes. Consult a dermatologist or healthcare provider if a birthmark changes in size, shape, or color. Immediate evaluation is also recommended if a birthmark becomes painful, itchy, bleeds, or develops a crust or scab. Developing new moles in adulthood also warrants professional assessment.
Early detection is important for better outcomes if skin cancer is present. If you have any concerns about a birthmark, it is always best to have it examined by a healthcare professional. They can accurately diagnose the type of birthmark and determine if further evaluation or monitoring is needed.