ConditionSkin, hair & nails
Blue Nevus (Blue Mole)
A blue nevus is a benign mole that looks blue, blue-gray or blue-black because its pigment cells sit deep in the skin, and light scattering through the skin makes the brown pigment appear blue. It is usually small, smooth, round and firm, often on the hands, feet, scalp or buttocks, and stays the same for years. Blue nevi are not dangerous. Because melanoma can also look dark blue or black, any new, growing or changing blue spot should be checked by a dermatologist.
Also called: Blue mole, blue naevus, common blue nevus, cellular blue nevus
At a glance
- What it is
- A benign mole made of pigment cells deep in the dermis, appearing blue.
- Who gets it
- Children and young adults most often. Slightly more common in women and people of Asian heritage.
- Typical look
- Small (under 1 cm), smooth, dome-shaped, uniform blue to blue-black.
- Types
- Common, cellular, and combined blue nevi. Malignant blue nevus is very rare.
- Treatment
- None needed. Removal if it changes, is large or the diagnosis is uncertain.
When to get help
See a doctor within a day or two
- A blue or black spot that is growing quickly, bleeding, ulcerating or forming a lump over weeks
Book a routine appointment
- A new blue or black spot after age 30
- A blue mole larger than 1 cm, or one that is changing in size, shape, color or height
- An irregular border, more than one color, or satellite spots around it
- A blue spot that you cannot explain, for example not a known pencil-lead or tattoo mark
Usually safe to manage at home
- A small, smooth, uniform blue mole that you have had unchanged for years (photograph it and check it a few times a year)
Why a blue nevus looks blue
Ordinary moles have pigment cells (melanocytes) near the skin surface, so they look brown. In a blue nevus, the melanocytes sit deep in the dermis. Light passing through the skin is scattered: longer red wavelengths are absorbed by the deeper pigment, while shorter blue wavelengths are reflected back. This optical effect, called the Tyndall effect, makes the brown melanin appear blue. Blue nevi are thought to come from melanocytes that did not finish their migration to the surface of the skin during development.
Types of blue nevus
| Type | Typical features | Notes |
|---|---|---|
| Common blue nevus | Under 1 cm, smooth, round, blue-black, on hands, feet, face or scalp | Most frequent type, very low risk |
| Cellular blue nevus | Larger, often 1 to 3 cm, firm nodule, often on the buttocks or lower back | Benign but can grow, usually removed for diagnosis |
| Combined blue nevus | Blue nevus combined with an ordinary brown mole | Two-toned appearance, may need biopsy |
| Malignant blue nevus | A melanoma arising in or resembling a blue nevus | Very rare, often a growing cellular blue nevus on the scalp |
Multiple blue nevi can rarely be part of an inherited syndrome called Carney complex, which also involves other pigmented spots and heart and hormone tumors.
Symptoms and appearance
- a single, well-defined blue, blue-gray or blue-black spot
- smooth surface, dome-shaped or flat
- firm to the touch
- usually painless and does not itch
- stable for many years
Blue nevi can appear at birth but most develop in childhood or young adulthood.
Blue nevus vs melanoma and other blue spots
| Lesion | Clues |
|---|---|
| Blue nevus | Small, symmetrical, uniform color, stable for years |
| Nodular melanoma | New or growing quickly, may be blue-black, raised, can bleed or crust |
| Melanoma metastasis to skin | New blue-black nodule in someone with previous melanoma |
| Pencil-lead or tattoo mark | Remembered injury, flat, does not change |
| Venous lake or blood blister | Compresses and lightens when pressed, often on lips or ears |
| Mongolian spot | Large, flat blue-gray patch on the lower back in babies, fades in childhood |
Because melanoma can look blue or black, dermatologists use the ABCDE checklist and evaluate any blue spot that is new in adulthood or changing. See moles for normal mole patterns.
Diagnosis
A dermatologist examines the spot with a dermatoscope. A blue nevus shows a structureless, uniform steel-blue color, which is reassuring. Features that prompt a biopsy include:
- a new lesion in an adult
- size over 1 cm or growth
- irregular shape, multiple colors or other structures under dermoscopy
- a nodule on the scalp
An excision biopsy (removing the whole spot with a small margin) allows a pathologist to confirm the diagnosis.
Treatment
- No treatment is needed for a typical, stable blue nevus.
- Surgical excision is done if the nevus is changing, is a cellular type, the diagnosis is uncertain, or for cosmetic reasons. Because the pigment is deep, shaving or laser treatment is not suitable; complete excision with stitches is standard.
- Monitoring: take a dated photo and compare every few months. Routine skin checks are reasonable if you have many moles or other risk factors. See skin cancer screening.
Outlook
Common blue nevi are benign and remain harmless for life. Cellular blue nevi are also benign but are usually removed because they are larger and can rarely be confused with melanoma. Malignant change is very rare.
Frequently asked questions
Is a blue nevus dangerous?
No. A typical blue nevus is a harmless mole that rarely changes. It looks blue because its pigment lies deep in the skin. A dermatologist should check any blue spot that is new in adulthood, larger than 1 cm, or changing.
Can a blue nevus turn into melanoma?
It is very rare. Malignant blue nevus is a rare type of melanoma that may arise from a cellular blue nevus, usually on the scalp. Most blue nevi stay the same for life. Watch for growth, bleeding or a change in shape.
What is the difference between a blue nevus and melanoma?
A blue nevus is usually small, round, smooth and uniform in color, and stable for years. Melanoma is more often new, growing, irregular in shape or color, or bleeding. Dermoscopy and, if needed, a biopsy tell them apart.
Should a blue nevus be removed?
Not usually. Removal is advised if it changes, is larger than about 1 cm, is a cellular type, looks unusual under dermoscopy, or bothers you cosmetically. Removal is a minor procedure under local anesthetic.
Why did a blue mole appear on my skin?
Blue nevi form when pigment cells settle deep in the skin rather than at the surface, often appearing in childhood or early adulthood. A new blue spot in later adult life should be checked, because it is less likely to be a simple blue nevus.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Moles, who gets them and types
- American Osteopathic College of Dermatology: Blue nevus
- DermNet: Blue naevus
- Skin Cancer Foundation: The ABCDEs of melanoma
- MedlinePlus (US National Library of Medicine): Moles