Atypical moles often stand out because they do not match a person’s other moles or because they have irregular features. Common characteristics include:

• Asymmetry (one half does not match the other)
• Border irregularity (notched, scalloped, or poorly defined edges)
• Color variation (mixtures of tan, brown, black, pink, or red)
• Larger size (often greater than 6 mm, though smaller lesions can still be atypical)
• Evolution (change in size, shape, color, or symptoms over time)
• Surface differences such as slight scaliness, bumpiness, or a combination of flat and raised areas
• Symptoms such as itching, tenderness, or bleeding, particularly when new or changing

Some atypical moles are present for years with minimal change, while others evolve slowly. A single “outlier” lesion that looks noticeably different from surrounding moles is often described as an “ugly duckling” mole and warrants evaluation.

Atypical moles develop from a combination of genetic tendencies and environmental factors. They are more common in individuals who have:

• A family tendency toward atypical moles or melanoma
• Many total moles overall
• History of intense or intermittent sun exposure, especially blistering sunburns
• Tanning bed exposure
• Lighter skin types, though atypical moles can occur in all skin tones

In many cases, atypical moles reflect how melanocytes respond to ultraviolet (UV) exposure and inherited traits. Importantly, atypical moles themselves are not “caused” by melanoma or definitively progress to melanoma, but their presence can be a marker of increased melanoma risk, which is why ongoing skin surveillance is often recommended.

Diagnosis begins with a focused history and a full skin examination. At Peak Skin Center, Dr. Thomas Knackstedt evaluates atypical moles by looking at overall mole pattern, identifying “ugly duckling” lesions, and using dermoscopy when helpful to assess pigment networks and structures not visible to the naked eye.

A mole may be recommended for biopsy when it has concerning clinical features, shows documented change, or does not fit the patient’s typical mole pattern. Biopsy allows a pathologist (dermatopathologist) to evaluate the architecture of the mole under a microscope and determine whether it is benign, atypical (dysplastic), or melanoma.

When a mole is labeled “atypical,” the pathology report commonly assigns a grade of atypia based on how abnormal the cells and overall mole structure appear:

Mild atypia

Cells show mild irregularities. Many mild atypical moles behave benignly and may not require further treatment beyond clinical monitoring, depending on whether the biopsy edges are clear and the clinical context.

Moderate atypia

Changes are more pronounced. Management can vary depending on the margins of the biopsy specimen, the lesion location, and the patient’s overall melanoma risk factors. Some moderate atypia lesions are re-excised to ensure complete removal, while others may be monitored when margins are clear and clinical suspicion is low.

Severe atypia

Cellular and structural changes are closer to melanoma on a spectrum, though not diagnostic of melanoma. Severe atypia is more commonly managed with complete excision to ensure the lesion is fully removed and to reduce the chance of missing an evolving melanoma.

Treatment depends on the degree of atypia, biopsy margins, and overall risk factors.

Observation and monitoring

For moles with mild atypia and reassuring clinical features, the most common approach is monitoring. This may include periodic full-body skin examinations and, in selected cases, photographic mole mapping or focused re-checks of specific lesions. Monitoring is especially important for individuals with multiple atypical moles or a family history of melanoma.

Complete removal (excision)

When a mole shows moderate to severe atypia, has involved or uncertain margins, or remains clinically concerning, complete removal is often recommended. Excision typically removes the remaining mole tissue with a small margin of normal skin and closes the area with stitches. The removed tissue is sent to pathology to confirm complete removal and to verify the diagnosis.

Re-biopsy or additional sampling (selected cases)

If a pathology report and the clinical appearance do not match well, or if the biopsy sample may not have captured the most concerning portion of a lesion, additional sampling may be recommended. This helps ensure an accurate diagnosis, particularly when severe atypia is reported or melanoma is a concern.

Ongoing prevention and risk reduction

Because atypical moles can be a marker of elevated melanoma risk, treatment plans often include prevention strategies such as consistent sun protection and regular surveillance. Dr. Thomas Knackstedt and the team at Peak Skin Center provide individualized follow-up intervals based on the number of atypical moles, prior skin cancer history, family history, and biopsy findings.