Dysplastic Nevus: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
April 24, 2026

A dysplastic nevus — also called an atypical mole or an atypical melanocytic nevus — is a non-cancerous skin growth made up of melanocytes, the cells that produce the pigment melanin. Dysplastic nevi differ from common moles because the melanocytes are arranged in an irregular pattern and look slightly abnormal under the microscope. Despite these changes, a dysplastic nevus is benign and does not pose an immediate health risk.

The importance of a dysplastic nevus is as a marker. People who have one or more dysplastic nevi are at somewhat higher risk of developing melanoma — a type of skin cancer — somewhere on their skin over the course of their life, even though an individual dysplastic nevus itself very rarely turns into cancer. This article will help you understand the findings in your pathology report for a dysplastic nevus — what each term means and why it matters for your care.

What causes a dysplastic nevus?

The exact cause of a dysplastic nevus is not fully understood, but both genetic and environmental factors are thought to play a role. Known risk factors include:

• Ultraviolet (UV) exposure — UV radiation from the sun or tanning beds damages the DNA in melanocytes and contributes to the development of dysplastic nevi, particularly on sun-exposed skin.
• Fair skin — Dysplastic nevi are more common in people with lighter skin, light-colored eyes, and red or blond hair.
• Family history — People with a close relative who has had dysplastic nevi or melanoma are more likely to develop them.
• Many moles — People with a larger total number of moles tend to have more dysplastic nevi.
• Atypical mole syndrome (also called dysplastic nevus syndrome or familial atypical multiple mole melanoma, or FAMMM) — A small number of families carry inherited mutations (such as in the CDKN2A gene) that cause multiple dysplastic nevi and a substantially higher lifetime risk of melanoma.

What does a dysplastic nevus look like?

Dysplastic nevi can appear anywhere on the body but are most often seen on the trunk, back, arms, and legs. Common features include:

• Irregular shape and border — The edges are often uneven or blurred and fade gradually into the surrounding skin.
• Mixed colors — A single lesion may contain several shades of brown, tan, pink, or red.
• Larger size — Dysplastic nevi are often larger than common moles, sometimes more than 5 millimeters across.
• Mixed texture — They may be flat, slightly raised, or have a combination — sometimes described as a “fried egg” appearance, with a raised central area surrounded by a flat, lighter rim.

Because dysplastic nevi can resemble early melanoma, any mole that changes in size, shape, or color, or that looks different from the other moles on your body (the “ugly duckling sign”), should be evaluated by a healthcare professional.

How is the diagnosis made?

A dysplastic nevus is diagnosed after a tissue sample is examined under the microscope by a pathologist. The sample is obtained by a skin biopsy. Because the pattern of cells across the entire lesion is important for the diagnosis, an excisional biopsy (the entire mole is removed) or a deep shave biopsy is usually preferred over a small punch biopsy. Under the microscope, the pathologist looks for two main features that distinguish a dysplastic nevus from a common mole. The first is architectural disorder — the overall arrangement of melanocytes is irregular, with single cells and small clusters (nests) of melanocytes at the base of the epidermis, nests that bridge between the downward extensions of the epidermis (rete ridges), and melanocytes extending beyond the main central area to form “shoulders” at the edges of the lesion. Around these areas, the tissue may show scar-like changes (fibroplasia) and a scattering of immune cells called lymphocytes. The second feature is cytologic atypia — the individual melanocytes look slightly abnormal, with nuclei that are larger, darker (hyperchromatic), or more irregular in shape than normal. Dividing cells (mitotic figures) are rare in a dysplastic nevus; when present, they raise concern for melanoma and prompt additional scrutiny. Imaging is not needed for dysplastic nevi because they are benign and do not spread.

Grade

Pathologists assign a grade to a dysplastic nevus based on the degree of atypia and architectural disorder seen under the microscope. The traditional grading system has three tiers:

• Mild dysplasia — The melanocytes show only slight irregularities, and the overall lesion looks close to a common mole.
• Moderate dysplasia — The melanocytes and overall architecture show more noticeable abnormalities, but still fall clearly short of melanoma.
• Severe dysplasia — The melanocytes show marked atypia and architectural disorder. These lesions can be difficult to distinguish from melanoma in situ, and the report may comment on features that were specifically considered and excluded.

Some pathologists and expert panels now use a simpler two-tier system in which mild dysplasia is classified as “low grade” and moderate-to-severe dysplasia as “high grade.” Both systems are in current use, and the terminology in your report reflects the lab’s preference.

It is important to emphasize that a dysplastic nevus of any grade is benign. Even a severely dysplastic nevus has a very low risk of turning into melanoma by itself. The main reason grading matters is that it guides decisions about whether further surgery is needed after a biopsy.

Margins

A margin is the edge of the tissue removed during a biopsy or excision. Pathologists examine margins under the microscope to see whether any nevus cells are present at the cut edge.

• Negative margin — No nevus cells are seen at the cut edge. The lesion is considered completely removed, and no further surgery is needed.
• Close margin — Nevus cells are near the cut edge but do not reach it. A close margin is common on small biopsies and is usually acceptable, particularly for mildly dysplastic nevi.
• Positive margin — Nevus cells are present at the cut edge. This means some of the lesion remains in the skin. For mildly dysplastic nevi, a positive margin can often be followed clinically. For moderately or severely dysplastic nevi, a second, wider excision may be recommended to remove any remaining abnormal cells and to rule out the possibility that a more concerning lesion is hidden at the edge of the biopsy.

Does a dysplastic nevus turn into cancer?

An individual dysplastic nevus very rarely turns into melanoma. Most melanomas arise in normal-appearing skin rather than from a pre-existing mole, and the lifetime chance that any single dysplastic nevus will progress to melanoma is very small.

However, having dysplastic nevi is a marker of a somewhat higher overall risk of developing melanoma somewhere on the body. The level of risk depends on how many dysplastic nevi a person has and on family history:

• One or a few dysplastic nevi — A slight increase in lifetime melanoma risk compared with the general population.
• Many dysplastic nevi — A higher lifetime risk, sometimes several times that of the general population.
• Many dysplastic nevi plus a family history of melanoma — The highest risk category, particularly in families with atypical mole syndrome (FAMMM).

For this reason, the most important response to a diagnosis of dysplastic nevus is regular, thorough skin surveillance — not worry about the individual lesion that was removed.

What happens after the diagnosis?

Most people who are diagnosed with a dysplastic nevus need no treatment beyond the original biopsy. The main focus after the diagnosis is on surveillance and sun protection.

Further surgery. For mildly dysplastic nevi with clear or close margins, no additional surgery is usually needed, even if small amounts of nevus are left behind. For moderately or severely dysplastic nevi with positive margins, your doctor may recommend a second excision to remove any remaining cells and ensure nothing more concerning was missed. Practice varies between centers, and your dermatologist will tailor the approach to the specific features of your lesion.

Skin surveillance. Regular full-body skin examinations by a dermatologist are recommended, especially for people with multiple dysplastic nevi or a family history of melanoma. How often depends on your personal risk profile — ranging from once a year for most people to every few months for those at the highest risk. Total-body photography and digital dermoscopy are sometimes used to help track existing moles over time.

Self-examination. Checking your own skin regularly is an important part of surveillance. The “ABCDE” features — asymmetry, border irregularity, color variation, diameter greater than 6 mm, and evolution (change over time) — are useful warning signs for melanoma.

Sun protection. Limiting UV exposure, using broad-spectrum sunscreen, wearing sun-protective clothing and a hat, and avoiding tanning beds are important steps to reduce the risk of developing new dysplastic nevi and of progressing to melanoma.

Genetic counseling. For people with many dysplastic nevi and a strong family history of melanoma or pancreatic cancer, referral to a genetic counselor may be appropriate to discuss testing for inherited conditions such as CDKN2A-related atypical mole syndrome.

Questions to ask your doctor

• Was the dysplastic nevus completely removed?
• What grade of dysplasia did my lesion show?
• Were the margins negative, close, or positive?
• Do I need a second excision, and if so, why?
• How does having a dysplastic nevus change my lifetime risk of melanoma?
• How often should I have a full-body skin examination, and by whom?
• Should I use total-body photography or digital monitoring to track my moles?
• What warning signs should I watch for when checking my own skin?
• Given my personal and family history, should I be referred to a genetic counselor?
• What sun-protection strategies do you recommend for me?
• Should my immediate family members also have a skin examination?