Indeterminate melanocytic proliferations of the conjunctiva

Purpose: The purpose of this study is to test the hypothesis that a subset of conjunctival melanocytic proliferations exists that cannot be reproducibly classified as benign, malignant, or indeterminate. Methods: Three groups of excisional biopsy specimens of conjunctival melanocytic proliferations were evaluated by 5 ophthalmic pathologists. These groups included lesions that were considered by the authors to represent benign (Group 1, n=5), malignant (Group 2, n=5) and indeterminate melanocytic proliferations (Group 3, n=5). The panel classified the same sections in all 3 groups in a randomized, masked fashion, first without and then with a clinical history of patient age, sex and race. The kappa statistic (k) was used to quantify the degree of agreement among observers. Results: There was strong concordance among the panel for both Group 1 (benign, k=0.76) and Group 2 (malignant, k=0.70) melanocytic proliferations. There was no concordance of the panel for Group 3 (indeterminate) lesions (k=-0.045). The concordance for Groups 1 and 2 and lack of concordance for Group 3 lesions were independent of knowledge of clinical history of age, sex, and race. Conclusions: A subset of melanocytic proliferations of the conjunctiva exists that cannot be reproducibly classified by pathologists as benign, malignant, or indeterminate.