Section Editor: Allison Osmond MD FRCPC
June 13, 2026
A nevus (plural: nevi) is the medical term for a growth or spot on the skin that develops from melanocytes, the cells that produce melanin, the pigment that gives skin and hair their color. Most nevi are harmless and are commonly called moles, although the term nevus covers a wide range of pigmented and non-pigmented growths. This article explains what a nevus is, describes the common types and what they look like under the microscope, and explains when a nevus might need attention, so you can better understand the findings in your pathology report.
What is the difference between a nevus and a mole?
The words “nevus” and “mole” are often used to mean the same thing, but they are slightly different. A nevus is the broad medical term that includes all types of melanocytic growths, whether present at birth or developing later in life. A mole is the everyday word for a common melanocytic nevus, usually a small pigmented spot on the skin. In other words, all moles are nevi, but not every nevus is what most people would call a mole.
What causes a nevus?
Most nevi develop from a combination of inherited tendency and sun exposure. The melanocytes in a nevus usually carry a single change (mutation) in a gene that controls cell growth; acquired moles most often carry a change in a gene called BRAF, while nevi present at birth more often involve a gene called NRAS. This change causes melanocytes to proliferate to a limited extent and then stop, which is why a nevus reaches a certain size and then remains stable. People who had more sun exposure, especially in childhood, and those whose family members have many moles, tend to develop more nevi over their lifetime.
Types of melanocytic nevi
There are many types of nevi, each with its own features. The most common types include:
- Junctional nevus — Grows at the junction between the epidermis (outer skin layer) and the dermis (the layer beneath it). It appears as a flat or slightly raised, evenly colored spot. See our article on the junctional nevus.
- Compound nevus — Grows both at the junction and within the dermis. It is usually raised, with a smooth or slightly bumpy surface. See our article on the compound nevus.
- Dermal nevus — Grows entirely within the dermis. It often appears as a raised, dome-shaped bump and may lose its color over time. See our article on the dermal nevus.
- Simple lentigo — A small, flat, evenly colored spot caused by an increased number of melanocytes.
- Lentiginous melanocytic nevus — A nevus in which the melanocytes are spread along the bottom of the epidermis in a row; it can resemble a simple lentigo but looks slightly different under the microscope.
- Dysplastic nevus — Has irregular borders, uneven color, and is sometimes larger than a common mole. Most do not become cancerous, but they may carry a slightly higher risk of melanoma. See our article on the dysplastic nevus.
- Nevus spilus — A light brown patch with darker spots scattered through it, often present at birth or appearing early in life.
- Special-site nevus — A nevus from areas such as the breast, armpit, scalp, or ear, which can look unusual under the microscope because of its location.
- Halo nevus — A mole surrounded by a ring of lighter or white skin, which happens when the immune system reacts against the melanocytes.
- Meyerson nevus — A nevus surrounded by a red, scaly, eczema-like rash that usually clears on its own.
- Recurrent nevus — A mole that regrows after being partly removed, often by shaving. The regrowth can look irregular but is typically benign.
- Combined nevus — A single lesion made up of two or more types of nevi, such as a blue nevus together with a compound nevus.
- Spitz nevus — A benign mole that is often pink, red, or tan and can resemble melanoma under the microscope. It is more common in children and young adults. See our article on the Spitz nevus.
- Acral nevus — A nevus on the palms, soles, or under the nails, which often looks different from moles elsewhere because of the special skin in these areas.
- Mucosal and genital nevus — A nevus on a mucous membrane, such as inside the mouth or on the genitals, which can look darker than other nevi.
- Blue nevus — Appears blue or gray because the melanocytes sit deep in the dermis. These are usually small, round, and benign. See our article on the blue nevus.
- Congenital nevus — Present at birth or appearing within the first year of life. These vary in size and color and may carry a small risk of melanoma, especially when very large (giant congenital nevi). See our article on the congenital nevus.
How is the diagnosis made?
Most nevi are recognized by a doctor based on their appearance and do not need to be removed or tested. When a nevus is removed, because it is changing, irritated, or being checked to rule out melanoma, the tissue is examined under the microscope by a pathologist after a biopsy or excision.
Under the microscope, a nevus consists of melanocytes arranged in small, well-organized clusters called nests. The location of the nests depends on the type of nevus: in a junctional nevus, they sit at the junction of the epidermis and dermis; in a compound nevus, they are found both at the junction and deeper in the dermis; and in a dermal nevus, they are entirely within the dermis. Pathologists also look for features that indicate a nevus is benign, including symmetry (the lesion looks the same on both sides), uniform color, and maturation, meaning melanocytes become smaller as they extend deeper into the dermis. These benign features are important because they help the pathologist tell a harmless nevus apart from melanoma.
Can a nevus turn into melanoma over time?
Most nevi never turn into melanoma. Some types, such as dysplastic nevi and large congenital nevi, carry a slightly higher risk. What matters most is change over time. Watching nevi for changes in size, shape, or color, or for symptoms such as itching or bleeding, is the best way to catch a problem early. If a nevus changes, a doctor may recommend further evaluation or removal.
What are the worrisome features of a nevus?
Certain changes in a nevus can be warning signs of melanoma and should be checked by a doctor. They are often summarized using the “ABCDE” rule:
- Asymmetry — One half of the nevus looks different from the other.
- Border irregularity — The edges are uneven, jagged, or blurred.
- Color changes — The nevus has more than one color or uneven pigmentation.
- Diameter — The nevus is larger than about 6 millimeters (the size of a pencil eraser).
- Evolution — The nevus changes in size, shape, or color, or develops itching or bleeding over time.
If you notice any of these changes, see your doctor for further evaluation.
Does a nevus need to be removed?
A nevus usually does not need to be removed unless it is causing symptoms such as pain or irritation, or it shows worrisome features that could suggest melanoma. Some people choose to have a nevus removed for cosmetic reasons. If your doctor is concerned about a nevus, they may recommend removing it and examining it under the microscope to confirm that it is benign. Whether or not a nevus is removed, regular skin self-checks and routine examination by a doctor are the best ways to notice any concerning change early.
Questions to ask your doctor
- Is my nevus benign, and what type is it?
- Did it show any unusual or atypical features?
- Was the whole nevus removed, or could some have been left behind?
- Is there any chance it could grow back as a recurrent nevus?
- Do I have any other moles that should be watched or removed?
- Do I have features that increase my risk of melanoma, such as many moles, dysplastic nevi, or a family history?
- What changes in a mole should prompt me to call you?
- How often should I have my skin checked?
- What can I do to protect my skin from sun damage?
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