Pathology

Histology, immunohistochemistry and electron microscopy have given us insights into the microanatomy of keloid scars. Compared to normal, non-fibroproliferative scarring, keloid scars show:

• slight thickening of a normally-restituted dermis
• thickened dermis
• increased density of blood vessels
• smaller fibrils of collagen
• more densely packed fascicles; thought to be broader than in hypertrophic scars
• a characteristic structure within the reticular dermis, the collagen nodule, which is a concentration of collagen longitudinally; it is relatively avascular, but is surrounded by an envelope of occluded microvessels; there is a high density of fibroblasts

There is a large degree of overlap of histological features between keloid and hypertrophic scars. Indeed, some authorities have suggested that the dynamic nature of change within the two clinical types of fibroproliferative scarring makes pathological distinction between them impossible; they may simply represent different time points on a continuum of abnormality.