We assessed the usefulness of silver staining of nucleolar organizer regions in the diagnosis of pigmented conjunctival tumors. Fifty-one biopsy specimens were silver stained to identify the nucleolar organizer regions. Nineteen nevi without atypia, three nevi with atypia, eight primary acquired melanosis lesions, and 14 melanomas were studied. In each specimen, silver staining of the nucleolar organizer regions was counted in 100 cells to yield an average of the silver staining of the nucleolar organizer region count. The mean silver staining of the nucleolar organizer region counts per cell was correlated with the degree of malignancy of pigmented conjunctival lesions as follows: nevi, 3.0; primary acquired melanosis, 3.2; nevi with atypia, 3.9; primary acquired melanosis with atypia, 5.0; and melanoma, 5.7 (Spearman correlation [rS] = .83, P = .0001; analysis of variance [ANOVA] F test = 20.9, P = .0001). A cutoff value of 4.0 (mean silver staining of nucleolar organizer regions per cell) will differentiate melanoma and primary acquired melanosis with atypia from other lesions (sensitivity, 100%; specificity, 96%). The silver staining of nucleolar organizer regions is a useful adjunct in determining the malignancy of pigmented conjunctival tumors.
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