A dermatofibroma is an very common skin growth. It is a small, firm bump on the skin. The dermis layer of skin contains nerve endings, glands, and vessels. The bump is an overgrowth of the tissue in the dermis layer. The bump is generally pinkish-brown in color. It is often found on the legs. Sometimes more than one appears. Generally, they are harmless and are not connected to skin cancer.

Layers of the Skin
Cut-away of the Skin
In dermatofibroma, the overgrowth occurs in dermis layer of the skin.
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The cause is unknown. Dermatofibromas sometimes appear after a minor injury to the skin. This can include an insect bite or a prick of a thorn.