Scar tissue that grows rapidly, like a tumour, and protrudes above the surrounding skin; a normal scar is only slightly thicker than the skin. A tendency to the condition is hereditary, and it is commoner in darker-skinned people and following infected wounds. The condition is difficult to treat, because new keloid tissue tends to form in the wound after surgery. Sometimes corticosteroids are injected, but in recent wounds this increases the danger of infection.