Although the exact cause for hair growth on moles is unknown, the National Cancer Institute explains that some moles have hair growing out of them because they were formed at or near birth. These moles are known as congenital nevi, and they are located deep within the tissue.
Many people have concerns that moles with one or more hairs growing from them are cancerous, but the National Cancer Institute says that moles with a hair growing out of them are actually significantly less likely to turn cancerous than regular moles. The article further explains that congenital nevus moles are typically present from childhood, so they are unlikely to change rapidly. Moles that appear suddenly are the ones that are more likely to be cancerous and should be examined by a dermatologist as soon as possible.
According to the Dermatology Institute and Skin Care Center, darker, larger or irregular moles are of particular concern whether they have hair growing out of them or not. However, the National Cancer Institute explains that those who have darker hair and skin tend to have darker moles, while those with lighter hair and skin have lighter moles, so dark coloration is not always an indication of a cancerous growth.