Black hair nevus is a type of pigmented nevus, which has different names due to its different shapes and sizes, such as “spot nevus”, “black hair nevus”, “animal skin-like nevus”, “giant nevus”, etc. “giant nevus” and so on. It is a benign tumor formed by the local aggregation of nevus cells. Most of them may be autosomal dominant and may also be related to ultraviolet radiation. Black hair nevus often grows on various parts of the body such as face, forehead, neck, chest, lower limbs, etc. It bulges the skin or is papillary in shape, locally black, with rough and uneven surface, and some have only few hairs on it, while some are thick and coarser and blacker than normal hairs. If the mole grows rapidly and becomes larger, its color becomes lighter or darker and brighter, with local itching, burning or pain, the surface is dehaired, blood can be seen on the hidden red, or it may break down and crust or even form a long-lasting ulcer. The enlargement of nearby lymph nodes or the appearance of some small satellite-like moles around a large mole suggest that the mole has the tendency to become malignant.