Conjunctival squamous intraepithelial neoplasia and its differential diagnosis.

Conjunctival squamous intraepithelial neoplasia (CSIN) represents the in situ precursor of squamous cell carcinoma. The graded severity of intraepithelial dysplasia is considered a measure of risk for progression to invasive carcinoma. The range of cytoarchitectural changes in CSIN overlaps those of reactive atypia, squamous epithelial papilloma and in situ sebaceous carcinoma. Pseudoepitheliomatous hyperplasia and benign hereditary dyskeratosis of the conjunctiva are conditions without risk of neoplastic transform that are potentially mistaken for CSIN.