A dermatofibroma is a common benign fibrous skin lesion due to a growth of skin cells called histiocytes. In some cases it arises at the site of a minor injury, especially an insect bite or plugged hair follicle.
Dermatofibromas most often occur on the legs and arms. Once developed, they usually persist for years. They appear as firm nodules, often dark brown in color and may occasionally be painful. In general, it is of cosmetic significance only and tends to persist long term. Usually only reassurance is needed. Sometimes the dark color can raise anxiety about melanoma; if there is any doubt about its nature, the lesion may be easily biopsied.
Dermatofibromas are benign lesions and may be left alone without treatment. If they are painful or bothersome (for example, easily traumatized by shaving) they may be removed with surgery. Other techniques include freezing the lump with liquid nitrogen to flatten it out.