Physiopathology and differential diagnosis of pterygium

Abstract

Pterygium is a fibrovascular injury of the inflamed conjunctival tissue that grows over the cornea in a triangular shape. It is explained by the deterioration and deletion of stem cells, which are involved in the regeneration of corneal epithelium but this proliferation is interrupted and inhibited by a hyperplasia of the conjunctival tissue. These findings share many characteristics with tumors and neoplasms, such as genetic alteration, fibroblast proliferation, inflammation, vascularization, invasion and recurrence after resection, which may coexist with secondary premalignant lesions and become hyperplasia, metaplasia, dysplasia, and, in the worst case, carcinoma. Tendency to malignity over the ocular surface usually occurs in the transition zone between the corneal and conjunctival epithelium. This transition zone is a vascular region in which stem cells are generated, which are responsible for the proliferation, self-maintenance and production of a large number of differentiated daughter cells. Therefore, it has been proposed that tumors can result from preexisting lesions such as pterygium. Similar clinical symptoms can generate differential diagnoses such as inflammation, degeneration and tumors. Clinical distinction, especially in areas with high exposure to ultraviolet radiation, can be difficult because they have similar presentation and location. Definitive diagnosis will be confirmed through histopathological examination of the conjunctival tissue.