A blue nevus is a benign (noncancerous) type of mole. It may be present at birth or a person can develop one later in life. Learn more in this article.

Blue nevi are a category of melanocytic tumors, which arise from the proliferation of dermal dendritic melanocytes to form an acquired pigmented mole. They are also called pigmented nevi ...

Slate gray nevi (previously known as Mongolian blue spots) are a type of birthmark that resembles a bruise. They are not harmful and often disappear at a young age.