Depending on the how advanced the condition is, pseudoepitheliomatous hyperplasia may be present.

The rete ridges are elongated and hyperplastic (pseudoepitheliomatous hyperplasia, which may be mistaken for carcinoma).

Diagnostic characteristics are most commonly found in the granulomatous stage and are described as being chronic inflammatory cells, Russell bodies, and pseudoepitheliomatous hyperplasia, and groups of large vacuolated histiocytes containing Klebsiella rhinoscleromatis (Mikulicz cells).

The differential for OSSN includes pterygium, pingueculum, papilloma, solar keratosis, lipoma, lymphoma, chronic blepharoconjunctivitis, inflammation, melanoma, ocular pannus, pyogenic granuloma, kaposi sarcoma, keratocanthoma, mucoepidermoid carcinoma, pseudoepitheliomatous hyperplasia, and adenocarcinoma.