Keloids. When skin is injured, fibrous tissue (called scar tissue) forms over the wound to repair and protect the injury. In some cases, scar tissue grows excessively, forming smooth, hard growths called keloids.Keloids can be much larger than the original wound, and are most commonly found on the upper chest and shoulders.eloid scars tend to be larger than the original wound itself. They may take weeks or months to fully develop. While keloid scars may be itchy, they are typically not harmful to your health. You may experience some discomfort or tenderness, or possible irritation from clothing or other forms of friction.