Dermatofibroma are common spots found frequently on the legs, but may occur on other sites such as the arms and trunk. They are often found following inflammation of normal skin eg. insect bites or ingrown hairs. They may be skin coloured or brown to brown-blue in colour. Characteristically they are very hard to the touch. While they can suddenly appear they are usually subsequently very slowly growing. They are benign and do not require treatment. However, like all skin spots, if they suddenly increase in size they should be reviewed by your doctor.