Oral epithelial dysplasia (OED) is a sign of squamous cell carcinoma (SCC) progression. The dysplastic squamous epithelial cells degrade the stroma resulting in an invasion of the dysplastic epithelial cells into the underlying connective.

Objectives: We aim to evaluate collagen fibers by using picrosirius red staining among different types of epithelial dysplasia and their correlation to clinical parameters.

Methods: Eighty cases of paraffin blocks were retrieved and classified into 4 groups; hyperkeratosis, mild epithelial dysplasia, moderate epithelial dysplasia and severe epithelial dysplasia. Three cases of focal fibrous hyperplasia were used as positive controls. Picrosirius-red staining technique and investigating under a polarized light microscope were performed. The results were interpreted according to collagen fibers birefringence; (1) orange-red represents mature collagen patterns and (2) green- yellow represents the small diameter and immature collagen. (3) mixed birefringent rays of group (1) and (2).

Results: In hyperkeratosis cases, collagen fibers in most areas showed mixed orange-red to green-yellow similarly to collagen stained in mild epithelial dysplasia. However, in moderate to severe dysplasia, collagen fibers were generally stained in green-yellow. From clinical data, the average age of female samples was higher than that of male in all 3 types of epithelial dysplasia. The tongue was the most commonly affected site (32.5%) with homogeneous leukoplakia as the most common clinical feature (48.8%).

Conclusions: This present study reveals the relationship between the difference of the maturation of collagen fibers and histopathological diagnosis. The increase grade of OED represented in green-yellow birefringence refers to immature collagen.