Ocular Surface Squamous Neoplasia

Ocular surface squamous neoplasia (OSSN) is an important pathological entity for clinicians since it closely mimics common conjunctival and corneal surface pathologies like pinguecula, pterygium, conjunctival granulomas, and cysts. OSSN should not be neglected because of its high potential to cause ocular and systemic morbidity. The history of OSSN dates back to 1860, when it was first described by Von Graefe. Since then, OSSN has been extensively studied with the evolution of new treatment modalities. OSSN can have purely conjunctival involvement, purely corneal involvement, or conjunctival tumors extending over the cornea. The malignancies can range from conjunctival intraepithelial neoplasia (CIN) to squamous cell carcinoma.  The squamous neoplasms have further been classified as non-invasive and invasive types. Pizzarello and Jakobiec first described the term CIN that is similar to gynecologic tumor terminology of intraepithelial neoplasia. They subclassified CIN as mild, moderate, and severe dysplasia based on the extent of involvement. The lesion with less than one-third conjunctival involvement is classified as mild, with the inner two-thirds is labeled as moderate, and full-thickness means severe dysplasia. Lee and Hirst were the first to propose a classification system for OSSN encompassing all carcinomatous and dysplastic lesions of the ocular surface. The classification is as follows-: 1. Benign OSSN- pseudotheliomatous hyperplasia, benign hereditary intraepithelial dyskeratosis and, papilloma. 2. Preinvasive OSSN - conjunctival/corneal intraepithelial neoplasms grades I–III. 3. Invasive OSSN- squamous carcinoma, mucoepidermoid carcinoma.