Keloid scars on the chest of a 68 year old male south Asian patient. A keloid scar is a scar that fills with the protein collagen. In a normal scar the collagen breaks down once the wound has healed, but this fails to happen during the formation of a keloid scar. The scar expands from its original boundaries, and continues to grow even after the wound has healed. Cryosurgery uses liquid nitrogen to freeze and shrink the scar tissue.