Final answer:
A thickened, raised scar due to excessive collagen formation is called a keloid. It is distinctive from other types of scars such as atrophic scars, which are sunken and typically result from conditions like acne, demonstrating how keloids project above the skin surface due to ongoing collagen synthesis post-healing.
Step-by-step explanation:
A raised, thickened scar that results from excessive collagen formation is called a keloid. Keloids occur when the healing process involves an overproduction of scar tissue, leading to a large, raised scar that extends beyond the original injury site. Unlike the sunken appearance of atrophic scars, which are typically associated with acne and chickenpox, keloids are significantly more elevated and are a result of continued collagen synthesis even after the wound has healed.
During the wound healing process, fibroblasts in the connective tissue produce a collagen matrix to repair the damaged area. However, for some individuals, fibroblasts continue to produce collagen, leading to a robust and often itchy or painful scar known as a keloid. This type of scar formation differs substantially from the healing of regular wounds, where collagen production ceases once the wound has sufficiently healed, resulting in a flatter scar.