by Iris Teo MD FRCPC
October 25, 2022
A keloid scar is a non-cancerous type of change that happens in the skin after an injury. The most common location for a keloid scar is on the upper back, shoulders, chest, and ear lobes. Keloid scars are sometimes referred to only as ‘keloids’.
Doctors do not fully understand why some people develop keloid scars after an injury and others do not. However, keloid scars are more common in people with darker skin. Tension in the skin during wound healing, older age, and wound infection have also been shown to increase the risk of developing a keloid scar.
The inside of a keloid scar is made up mostly of a protein called collagen. Collagen is produced by specialized cells called fibroblasts as part of the normal healing process. However, in some people, fibroblasts make too much collagen. The extra collagen forms a lump that grows beyond the initially injured area forming a keloid scar.
Pathologists make this diagnosis after a tissue sample from the area is examined under the microscope. Keloid scars are usually much larger than the original site of injury. Pathologists look for broad, uniform, bright pink bundles of collagen in the dermis. Some consider these bundles to look a bit like a rope. The fibroblasts can look a little bigger than normal, and individual fibroblasts can be seen more easily between these bundles. Features associated with cancer are not seen. The epidermis over the keloid scar is typically normal.