Keloid scars are excessively thick and fibrous, tumour-like growths that extend beyond a wound's original limit. While not dangerous, keloid scar may itch, cause pain or be tender to the touch. Over time, they can develop claw-like projections into the surrounding skin. In the worse cases, they can be quite disfiguring.
No one understands why keloid scars form and while surgery (traditional and cryosurgery) can remove keloids, they often return. Whatever the cause, there does appear to be a genetic component. This type of scarring is found most often in people of African and Asian origins and also seems to run in families.