The blue nevus is a solitary blue-colored mole that can present at birth or develop later on in life. It can remain unchanged throughout the duration of a person’s life. The blue color, or ceruloderma, is caused by the Tyndall effect when light is preferentially scattering shorter wavelengths by melanin found in the dermis of the skin. It is unclear at this time as to whether there is a genetic component associated with a blue nevus. Since it is commonly found in Asian populations and in women more than in men, some suggest a genetic association. The blue nevus can be found on many areas of the body; however, most have been found on the head and neck, sacral area, back of the hands, and feet.
A blue nevus can vary in appearance and be categorized as either a common blue nevus or a cellular blue nevus. The common blue nevus is usually flat or dome-shaped with a smooth surface. The size can range between 0.5-1cm with the color varying from being blue-gray to blue-black. On the other hand, a cellular blue nevus is larger, at least 1 cm in diameter, and more nodular. The size of a cellular blue nevus can also get larger with time and the surface of the nevus can even ulcerate.
The diagnosis can be made by visual inspection alone. Although most cases of blue nevi are benign, there is a small possibility that a cellular blue nevus can undergo malignant transformation and become a malignant cellular blue nevus (MCBN). Thus, a biopsy of any changing or suspicious lesion should be done. Differential diagnoses to consider include malignant melanoma, pigmented dermatofibroma, metastasis, thrombosed plantar wart, or a tattooing effect.
If removal of a blue nevus is desired, it can be done through an excision. If there is evidence of a malignant cellular blue nevus, re-excision may need to be considered.
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