Blue nevus (also known as a blue mole) is a type of benign acquired nevus. These small blue-gray or blue-black papules represent an aggregate of melanocytes in the upper and mid-dermis. Blue nevi usually develop in young adulthood and are more common in women and in those of Asian descent.
Melanocytes originate embryologically in the neural crest and then migrate to the dermal-epidermal junction or to the hair bulb. Blue nevi are hypothesized to arise from melanocytes that fail to complete their developmental journey and instead reside and proliferate in the dermis. Dermal melanocytes reflect low-wavelength blue light but absorb higher wavelength light, a phenomenon known as the Tyndall effect. This accounts for the characteristic blue hue of the lesion. Somatic mutations in GNAQ mutations have recently been found in the majority of blue nevi.
A variant of blue nevus, the cellular blue nevus, is typically larger (1-3 cm in diameter) than a common blue nevus (<1 cm), solitary, and has a predilection for the buttocks or sacrococcygeal region. Malignant blue nevi are rare and tend to arise in cellular blue nevi, especially those on the scalp. Blue nevi are also one of the most common components of combined nevi. Another variant, the epithelioid blue nevus, may be associated with Carney complex (lentigines, atrial myxoma, mucocutaneous myxoma, and nevi).
A blue nevus is a type of mole that appears blue. Blue nevi (plural) appear to be blue-gray or blue-black and are caused by melanocytes (cells that produce pigment) that group together in the middle layer of the skin. They look blue because of where they are located in the skin. This is a benign mole that is not cancerous. However, since these moles look similar to more dangerous moles, like melanoma, they are sometimes biopsied just to confirm the diagnosis.
Who’s At Risk
Blue nevi are more common in women and individuals of Asian decent. They tend to first show up in childhood and adolescence.
Signs & Symptoms
These blue-gray or blue-black moles can appear anywhere on the body but are most common on the face, scalp, hands, and feet. They are usually no larger than a pencil eraser, appear round or oval, and are evenly colored.
There is a form of blue nevus called cellular blue nevus, which is typically larger than a blue nevus and is usually the size of a quarter. They tend to occur on the scalp, lower back, and buttocks. The cellular blue nevus has a very rare tendency to become cancerous.
There are no symptoms associated with blue nevus or cellular blue nevus.
Since these moles can appear anywhere on the body, watch them carefully to monitor for any change in color, size, or shape, since these changes can be signs of a more concerning mole.
When to Seek Medical Care
Since blue nevi and cellular blue nevi look similar to the more serious skin cancer melanoma, a skin biopsy can be done to confirm the diagnosis if there is any doubt. Go to your doctor as soon as possible if the mole is growing larger or changing color or shape.