Impression Cytology in the Diagnosis of Ocular Surface Melanocytic Lesions

The aim of this case series was to describe the results of impression cytology (IC) in clinically diagnosed ocular surface melanocytic lesions. Impression cytology (IC) was conducted for 18 patients with the clinical diagnosis of an ocular surface melanocytic lesion, using cellulose acetate strips and Periodic acid Schiff‑Papanicolaou staining. For those cases with atypical cells on IC or at patient’s request, excisional biopsies of lesions were performed and subjected to histopathological analysis. Agreement between clinical diagnoses and IC results and between IC results and histopathology were evaluated. Clinical diagnoses were nevi in 13, conjunctival choristoma versus amelanotic nevus in 1, primary acquired melanosis (PAM) with atypia/melanoma in 2, and atypical nevus versus pigmented conjunctival intraepithelial neoplasia (CIN) in 2 cases. IC results showed a benign nevus in 15, PAM with atypia/melanoma in 2, and CIN versus an atypical epithelioid type melanocytic lesion in 1 case. IC results were consistent with the clinical diagnoses in 16 cases (Cohen’s kappa index = 0.84) and excluded CIN in 1. Histopathology in 7 cases disclosed benign melanonevus in 4, malignant melanoma in the context of PAM with atypia in 2, and CIN in 1 case. There was a relatively high correlation between the histopathologic results and the IC features (Cohen’s kappa index = 0.76). By showing typical cytomorphological characteristics of ocular superficial layers, IC diagnosed the true nature of melanocytic ocular surface lesions in the most cases in this case series. Based on the fact that IC does not substitute histopathology, given the high correlation between results of IC and histopathology, it can be of excellent help in diagnosis and management of ocular surface melanocytic lesions.