Keloids show regional distribution of proliferative and degenerate connective tissue elements.

Keloids, formed by the deposition of excessive scar tissue, are characterised by the presence of thick hyalinised collagen bundles. Contradictory reports about keloid morphology include: hyperproliferation of dermal fibroblasts versus few fibroblasts; rich as opposed to poor vascularisation; dilated against occluded microvessels; distinct collagen nodules versus their absence, and elevated levels of types I and III collagen as opposed to no change when compared with normal dermis. This study attempted to clarify the controversies concerning keloid morphology by examining entire keloids and establishing baseline histological characteristics. Keloidal specimens from 32 patients were processed and comprehensively examined using light microscopy. The results of the study showed that keloids comprise many distinct regions, categorized as the zone of hyalinising collagen bundles, fine fibrous areas, area of inflammation, zone of dense regular connective tissue, nodular fibrous area and area of angiogenesis. The microvascular supply to each of these regions was impaired and features of degeneration and necrosis of keloid fibroblastic cells and microvessels were ubiquitous. Impairment of the healing stage of chronic inflammation, inefficient healing by fibrosis, multiple and exaggerated phases of vascular and fibrous granulation and remodelling stages manifest in keloid formation. The uneven distribution of cells may be due to the generation of traction forces by keloid cells. These forces also modify DNA and protein synthesis, leading to an overproduction of extracellular matrix components. This study provides a structured basis for future ultrastructural and immunocytochemical research of keloids and other fibroproliferative disorders. 2009 S. Karger AG, Basel.