What is a thick scar that results from excessive growth of fibrous tissue called?

A thick scar resulting from excessive growth of fibrous tissue is called a keloid. Keloids occur when the body produces too much collagen during the healing process, leading to an overgrowth of scar tissue that extends beyond the boundaries of the original injury.

Keloids can appear raised, smooth, and shiny, and they often have a reddish or darker color compared to the surrounding skin. They can occur anywhere on the body but are more common in areas such as the chest, shoulders, and earlobes.

In contrast, hypertrophic scars also involve an overgrowth of tissue but remain confined to the original injury site, typically flattening over time. Other types of scarring, such as contractures and atrophic scars, have different characteristics: contractures usually result from the tightening of skin that restricts movement, especially after burns, while atrophic scars are depressed scars that result from conditions that cause loss of underlying tissue, such as acne or chickenpox. Thus, keloids are specifically identified by their excessive growth beyond the original injury, making this the correct answer.