Dermatofibroma mostly occurs in women. It is also called histiocytoma. It generally forms as a reaction to previous injuries like insect bites, thorn pricks etc. They are composed of disordered collagen. This particular disease is nothing but the occurrence of nodules on the skin mainly on leg part. They are generally in yellow brown colour and sometimes it is quite dark. This disease does not show any symptom. Dermatofibroma mainly occurs in young adulthood. It feels like hard lumps under the skin. They are harmless and has no connection to skin cancer. It can cause little discomfort, itching and tenderness.