A blue nevus is a benign type of mole. It may be present at birth or develop as a person ages. Doctors refer to more than one blue nevus as blue nevi.
There are several different types of blue nevi. Common blue nevi are benign and will remain unchanged throughout a person’s life. However, there is a rare chance that a cellular blue nevus may change into a form of melanoma.
In this article, we look at the causes and risks of a blue nevus and discuss when to get advice from a doctor.
A common blue nevus presents as a smooth oval or circular mole. A blue nevus is typically blue or gray, but it can sometimes be yellowish-brown.
The main characteristics of a common blue nevus include:
- round or oval shape
- small size
- smooth in appearance
- a flat or elevated surface
- a diameter of around 1–5 millimeters (mm)
Another type of blue nevus, the cellular blue nevus, differs slightly in appearance. In comparison with the common blue nevus, the cellular blue nevus is more likely to:
- appear raised
- be a larger size — about 1–3 centimeters (cm)
- become malignant
A blue nevus tends to occur as a solitary mole, which means that a person is unlikely to have more than one in a particular area of the skin.
Blue nevi can occur anywhere on the body, but they are most common on the:
The type of blue nevus will determine how and where it presents. The different types include:
- common blue nevus
- subungual blue nevus
- cellular blue nevus
- combined blue nevus
- amelanotic blue nevus
- epithelioid nevus
- sclerosing (desmoplastic) blue nevus
A blue nevus does not usually require investigation. However, people should examine their skin regularly to check for any subtle changes to the mole, which may signal early signs of cancer.
Typically, a doctor can diagnose a blue nevus through a visual examination of its characteristics.
If a doctor needs more evidence, they may use a dermatoscopy to check for a pattern consistent with a blue nevus. If a dermatoscopy is insufficient to diagnose a blue nevus, a doctor may perform an excision biopsy.
A common blue nevus is usually benign, remains unchanged throughout life, and does not lead to any complications.
In rare situations, a cellular blue nevus may develop into a form of melanoma called a malignant cellular blue nevus. For this reason, a doctor will likely recommend removing a blue nevus that is:
- changing in shape
- growing bigger
- larger than 1 cm
- on the scalp
A person may decide to have their doctor remove a blue nevus for cosmetic reasons. However, a person should check with their insurance provider, as they may not cover cosmetic operations.
A person should see their doctor if:
- a new blue nevus appears randomly on the skin
- they notice an existing blue nevus changing in shape, size, or color
- the blue nevus is larger than 1 cm in diameter
- the blue nevus is itchy, painful, oozing, or bleeding
People should also regularly examine their own skin. The American Cancer Society recommend that people check their skin once a month. If a person discovers anything that is unusual or causes them concern, they should talk to their doctor about their findings.
It is unclear what causes a blue nevus. Certain cells seem to remain near the skin’s surface and cause a bluish mole to appear on the skin.
Although nearly anyone may develop a blue nevus, they are more likely to appear in females than in males. Blue nevi are also more prevalent in Asian populations.
Most blue nevi are benign, but there is a chance that a cellular blue nevus may develop into a form of melanoma. However, this is rare.
If a person sees their doctor about a blue nevus, the doctor will compare the characteristics of the mole against other similar looking conditions, such as:
- a dermatofibroma
- a combined nevus
- a traumatic tattoo
- cutaneous metastasis
- Kaposi’s sarcoma
- a vascular lesion, such as a venous lake
A blue nevus is a small bluish mole that will typically last the person’s lifetime. The only treatment is to remove the mole surgically, although this is not usually necessary.
In rare cases, a blue nevus may develop into melanoma. If a doctor suspects that a blue nevus might become cancerous, they may recommend removing it.
A person may also opt for the removal of a blue nevus for cosmetic reasons.
Usually, there are no symptoms or complications associated with having a blue nevus.