Table 2.

Histological staging of oral submucous fibrosis

Group	Histological features
Group I - very early	Fine fibrillar collagen network interspersed with marked edema, blood vessels dilated and congested, large aggregate of plump fibroblasts with abundant cytoplasm, inflammatory cells mainly PMN with few eosinophils. Epithelium normal, with occasional hyperplasia
Group II - early	Juxta-epithelial hyalinization with collagen present as thickened but separate bundles, blood vessels dilated and congested, moderate number of young fibroblasts, inflammatory cells mainly PMN, eosinophils, and occasional plasma cells. Epithelium shows flattening/shortening of rete pegs with varying degree of keratinization
Group III - moderately advanced	Juxta-epithelial hyalinization is present. Faintly discernible collagen bundles separated by very slight, residual edema. Muscle fibers interspersed within collagen fibers reveal the beginning of degeneration and irregularity of striae. Blood vessels constricted, mature fibrocytes with scanty cytoplasm, and spindle-shaped nuclei. Inflammatory cells, mainly lymphocytes and plasma cells. Epithelium markedly atrophic with total loss of rete pegs
Group IV - advanced	Collagen hyalinized as a smooth sheet eliminating all evidences of individual bundles. Extensive fibrosis obliterating the mucosal blood vessels and eliminating melanocytes. Fibroblasts markedly absent within hyalinized zones. Extensive degeneration of muscle fibers. Total loss of rete pegs with mild-to-moderate atypia

PMN: Polymorphonuclear