A blue nevus (plural nevi) is a specific type of mole that can occur anywhere on the skin. It is called "blue" because its black-brown melanin pigment resides deeper in the skin. This, like a black tattoo, can make them look bluish. While blue nevi are benign, they can rarely transform into a melanoma known as blue nevus-like melanoma or formerly malignant blue nevus.
Typically, it is a longstanding blue nevus that starts changing that should prompt examination and biopsy. Specific warning signs include:
Diagnosis: To distinguish these from benign blue nevi, a biopsy and histologic examination are required.
Blue nevus-like melanoma is ultra-rare, accounting for <1% of all melanoma cases. There is no evidence that blue nevi transform to melanoma more or less frequently than common nevi; rather, blue nevi are simply less frequent in the general population. This lower "baseline" frequency of the precursor (the blue nevus) likely explains the rarity of the resulting melanoma.
Blue nevus-like melanoma and uveal (eye) melanoma are biologically closely related, if not identical. They share several defining features:
Because these diseases are virtually identical in their molecular makeup and behavior, they require specialized treatment approaches that differ from standard skin melanoma.
In most cases, yes. A blue mole, medically known as a blue nevus, is usually a normal and benign skin lesion. Many people have one or more blue nevi, and they often appear during childhood or early adulthood. Although most blue moles are harmless, it is still important to monitor them for any unusual changes. Any mole that grows quickly, changes color or shape, becomes painful, or begins to bleed, should be evaluated by a dermatologist as soon as possible.
Yes, but this is rare. A blue mole, or blue nevus, is typically a benign lesion that remains stable and harmless throughout a person’s life. However, in uncommon cases melanoma can develop within or from a pre-existing blue nevus, or it may appear as a melanoma that closely resembles one. When this occurs, it is often described medically as blue nevus-associated melanoma or blue nevus-like melanoma.
Blue nevus-like melanoma is a rare form of melanoma that resembles a blue nevus, either in its appearance on the skin or under the microscope. Because it can look similar to a benign blue nevus, distinguishing between the two can sometimes be challenging. Unlike a benign blue nevus, blue nevus-like melanoma is malignant and has the potential to grow quickly, invade deeper tissues, and spread to other parts of the body. Dermatologists typically recommend a biopsy and detailed pathological examination to confirm the diagnosis.
Doctors usually begin with a skin examination and dermoscopy, a tool that allows them to closely examine the patterns and structures within a mole. Because some lesions can appear very similar, further testing is often needed. In many cases, a biopsy is required to determine whether the lesion is benign or cancerous. During a biopsy, a sample of the mole is removed and examined by a pathologist, often using special staining techniques and molecular tests to confirm whether the lesion is a blue nevus or melanoma.
A blue nevus should be evaluated by a dermatologist if it changes in size, shape, color, or texture, or if it becomes symptomatic - such as causing pain, itching, bleeding, or ulceration. People who have many moles, a personal or family history of melanoma, or other skin cancer risk factors may benefit from regular skin exams. Early evaluation helps ensure that any suspicious lesion is identified and treated as quickly as possible.
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