Moles, medically known as nevi, are common skin growths that develop when pigment-producing cells called melanocytes grow in clusters. Most moles are benign and pose no health risk, appearing as small, uniform, round, or oval spots. The term “precancerous mole” refers to a specific type of nevus whose cells show abnormal changes that increase the risk of developing melanoma, the most serious form of skin cancer. A precancerous mole itself is not cancer; rather, it signals an elevated risk profile that warrants careful attention and monitoring.
Defining Atypical Moles
The medical term for a precancerous mole is a Dysplastic Nevus (DN), which is clinically and histologically different from a common nevus. Under a microscope, a DN exhibits architectural disorder (abnormally arranged melanocytes) and cytologic atypia (irregular-looking melanocyte cells). These features place the Dysplastic Nevus on a continuum between a benign mole and melanoma.
The presence of DNs is a well-established risk factor for melanoma, with individuals having multiple atypical moles facing up to a 10-fold increased risk compared to the general population. Pathologists grade the cellular changes found in a biopsy as mild, moderate, or severe atypia, with higher grades carrying greater risk.
Identifying Features of Concern
Atypical moles can often be distinguished from common moles by visual characteristics. Dermatologists use the ABCDE mnemonic to help patients identify features that should prompt a professional examination.
- A: Asymmetry. One half of the mole does not match the other half.
- B: Border. The border is often irregular, poorly defined, or notched.
- C: Color Variation. The mole displays multiple shades of brown, tan, black, or even red, white, or blue within the same lesion.
- D: Diameter. The mole is typically larger than six millimeters, roughly the size of a pencil eraser.
- E: Evolving. This represents any change in the mole’s size, shape, color, or elevation over time. New symptoms like itching, tenderness, or bleeding also fall under this category.
People with many moles should also look for the “ugly duckling” sign—any mole that looks noticeably different from all the others on their body. Noticing any of these features warrants a consultation with a dermatologist.
Monitoring and Management
When a potentially atypical mole is identified, the first step is typically a detailed dermatological examination. During this check, a professional may use a specialized handheld device called a dermoscope, which magnifies the mole and uses polarized light to visualize structures beneath the skin’s surface that are invisible to the naked eye. This non-invasive tool helps the dermatologist better assess the architectural patterns and color distribution within the lesion.
For any mole that appears highly suspicious, a definitive diagnosis requires a biopsy, where a sample of the mole is surgically removed and sent to a lab for microscopic analysis. The results of the biopsy, specifically the grade of atypia, guide the subsequent management strategy. Moles diagnosed with mild or sometimes moderate atypia, especially in low-risk patients, are often managed with close photographic surveillance, known as “mole mapping.”
This surveillance involves taking baseline and follow-up images to track subtle changes over time, often scheduled for every 3 to 12 months depending on the patient’s overall risk profile.
Conversely, moles diagnosed with severe atypia, or any mole that shows concerning clinical changes, are usually treated with complete surgical excision. This procedure removes the entire mole and a small surrounding margin of healthy skin to ensure all atypical cells are gone. Individuals with a history of atypical moles should commit to a schedule of regular, full-body skin checks with a dermatologist and perform monthly self-examinations to catch any new or changing lesions as early as possible.