Dermatofibromas are firm bumps, or nodules, that form in the deep layers of the skin. Dermatofibromas are harmless and common. They tend to occur in response to an injury, such as an insect bit or ingrown hair. This makes them more likely to appear on the arms and legs. Dermatofibromas may persist indefinitely.
They can appear pink or dull red, or can resemble a mole (nevus). They are usually small (about a quarter- to a half-inch wide) but can grow to be over an inch in diameter. When pinched, dermatofibromas tend to create a dimple on the skin where the nodule attaches to the upper layers of the skin.
There is no prevention if the skin responds to injury by producing a dermatofibroma.
They are benign lesions that do not require treatment. If they are painful or their presence is bothersome (for example - easily traumatized by shaving) they can be removed with surgery.