Section Editor: Allison Osmond MD FRCPC
June 13, 2026
A blue nevus is a common, noncancerous (benign) skin growth made up of cells called melanocytes. Melanocytes are the cells in the skin that make melanin, the pigment that gives skin its color. A blue nevus gets its distinctive blue or blue-gray color from melanin that sits deep in the dermis (the layer of skin beneath the surface). When light passes through the skin, the deep pigment scatters it in a way that looks blue, an effect known as the Tyndall effect.
Blue nevi can appear anywhere on the body and are most often found on the hands, feet, scalp, buttocks, and face. A blue nevus is harmless, and it is one of the reassuring findings that can appear on a skin pathology report. This article explains what a blue nevus is, what the findings in your report mean, and why this growth is considered safe.
What causes a blue nevus?
A blue nevus forms when melanocytes collect deep in the dermis instead of near the surface of the skin, where they are usually found. Most blue nevi carry a single change (called a mutation) in a gene named GNAQ or GNA11, which drives this deep collection of pigment-producing cells. Unlike many common moles, blue nevi are not closely linked to sun exposure. Most blue nevi appear during childhood or adolescence, although some are present at birth and others develop later in adulthood.
What are the symptoms of a blue nevus?
A blue nevus usually causes no symptoms. Most are small, round or oval, and slightly raised, with a smooth surface and a single, even blue or blue-gray color. They tend to stay the same size and shape for many years. A blue nevus does not normally itch, bleed, or change quickly. Any mole that changes in size, shape, or color, or that begins to itch or bleed, should be checked by a doctor.
How is the diagnosis made?
Many blue nevi are recognized by a doctor based on their appearance and do not need to be removed. When a blue nevus is removed, because it is changing, is being checked to rule out melanoma, or for cosmetic reasons, the tissue is examined under the microscope by a pathologist after a biopsy.
Under the microscope, a blue nevus is made up of spindle-shaped and branching (dendritic) melanocytes that lie deep within the dermis and contain a large amount of melanin. Cells that have taken up loose pigment, called melanophages, are often seen nearby. Unlike many other moles, a blue nevus does not show nests of melanocytes at the junction between the epidermis and dermis. A more cellular variant, called a cellular blue nevus, is larger and contains more tightly packed cells; it is still benign but is examined carefully because it can occasionally look concerning. To confirm that the cells are melanocytes and to help separate a blue nevus from melanoma, the pathologist may use immunohistochemistry (special stains that highlight particular proteins in the cells).
Can a blue nevus turn into melanoma?
The chance that a blue nevus will turn into melanoma is very low. A rare cancer called malignant blue nevus (a form of melanoma) can develop within or resemble a blue nevus, most often a long-standing cellular blue nevus, but this is uncommon. Because of this rare possibility, a blue nevus that grows, changes color, develops an irregular border, or begins to itch or bleed should be examined by a doctor. When the microscopic features are unusual, the pathologist may ask a dermatopathologist (a pathologist who specializes in skin diseases) to review the slides to ensure the growth is benign.
What happens after this diagnosis?
In most cases, a blue nevus needs no further treatment. It is harmless and can simply be left in place and watched for change. When a blue nevus is removed, it is usually for one of the following reasons:
- Change in appearance — A mole that has changed in size, shape, or color, or developed an irregular border, may be removed so it can be examined under the microscope to rule out atypical cells or, rarely, melanoma.
- Uncertain diagnosis — If the growth is difficult to tell apart from melanoma or another skin lesion by eye, removal allows a definite diagnosis to be made under the microscope.
- Irritation — Moles in areas where clothing or jewelry rubs against the skin may be removed to prevent discomfort or repeated injury.
- Cosmetic reasons — Some people choose to have a mole removed because of where it is or how it looks.
When a blue nevus is removed only in part, a few melanocytes can be left behind at the edge of the sample and may grow back, a harmless situation called a recurrent nevus. A recurrent nevus can look irregular under the microscope, so it helps your doctor to know if the area was treated before. Whether or not a blue 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
- Was my growth a blue nevus, and was it the common type or a cellular blue nevus?
- Did the pathologist see any atypical or unusual features?
- Was the whole nevus removed, or could some of it have been left behind?
- Is there any chance it could grow back as a recurrent nevus?
- Was a dermatopathologist asked to review my slides?
- Do I have any features that increase my risk of melanoma, such as many moles or a family history?
- How often should I have my skin checked?
- What changes in this spot should prompt me to call you?
- Do I need any follow-up because of this result?
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