Table 1.

Histopathological classification of OSF

Very early stage (Grade I):	Early stage (Grade II):	Moderately advanced stage (Grade III):	Advanced stage (Grade IV):
❖ A finely fibrillar collagen, dispersed with marked edema. ❖ The fibroblastic response is strong. ❖ The blood vessels are sometimes normal, but more often they are dilated and congested. ❖ Inflammatory cells, mainly polymorphonuclear leukocytes with an occasional eosinophil are present.	❖ The juxta-epithelial area shows early hyalinization. ❖ Plump young fibroblasts are present in moderate numbers. ❖ The blood vessels are dilated and congested. ❖ The inflammatory cells are mostly mononuclear lymphocytes, eosinophils and an occasional plasma cell.	❖ The collagen is moderately hyalinized. ❖ The fibroblastic response is less marked, the cells present being mostly adult fibrocytes. ❖ Blood vessels are normal or constricted. ❖ The inflammatory exudates consist of lymphocytes and plasma cells, although an occasional eosinophil is seen.	❖ The collagen is completely hyalinized. ❖ The hyalinized areas are devoid of fibroblasts. ❖ Blood vessels are completely obliterated or narrowed. ❖ The inflammatory cells are lymphocytes and plasma cells.