Blue nevus

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A blue nevus is a colored mole that usually looks like a single blue-black bump with clear borders. The blue color happens because the pigment is located deep in the skin. The cause is unclear. It is diagnosed by examining the skin and may use dermoscopy; sometimes a biopsy is done, and sometimes the lesion is surgically removed. The outlook is generally good, but there is a small chance it could turn into skin cancer. Conditions that can look similar include dermatofibroma and melanoma. Blue nevi are more common in women. It was first described in 1906 by Tièche, a student of Jadassohn. There are different types, including dendritic and cellular blue nevi.