A dermatofibroma, also known as a fibrous histiocytoma, is a benign (non-cancerous) skin growth that appears as a small, hard bump.
An accumulation of fibrous tissue and immune cells in the skin causes dermatofibromas. The exact cause of this accumulation is unknown, but it is thought to be related to skin injuries, such as a bug bite or scratch. Some people may develop multiple dermatofibromas, while others may only have one. These growths are not cancerous, but they do not go away on their own.
Dermatofibroma is most commonly found on the legs but can also occur on the arms, trunk, and other body parts. Dermatofibromas are typically small, measuring less than one centimeter in diameter, and are brown, skin-colored, or pink. They are usually firm to the touch and do not move around when pressed. They may also feel itchy or painful, although this is uncommon.