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J. J. Augsburger, Z. M. Corrêa, N. Trichopoulos; Size Overlap Between Choroidal Nevi and Choroidal Melanomas. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4795.
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© ARVO (1962-2015); The Authors (2016-present)
To use plotted frequency distributions of tumor size to estimate the overlap between large choroidal nevi and small choroidal melanomas.
Frequency distributions of largest linear diameter and thickness of choroidal nevi and choroidal melanomas were plotted from cases in the author’s private practice and published data. Relative total frequencies of choroidal nevi and melanomas were estimated from published epidemiological data. The relative frequency distributions of choroidal nevi and melanomas were computed from the combined information and plotted together to illustrate the extent of overlap between large nevi (ones over 7 mm in diameter and over 2 mm in thickness) and small melanomas (ones under 10 mm in diameter and under 3 mm in thickness).
Choroidal nevi have a mean basal diameter of about 3.0 mm (std. dev. = 0.67 mm) and a mean thickness of about 0.6 mm (std. dev. = 0.13 mm). Over 95% of choroidal nevi are <5 mm in basal diameter and <1 mm in thickness. In contrast, choroidal melanomas have a mean basal diameter of about 12.0 mm (std. dev. = 3.0 mm) and a mean thickness of about 6.5 mm (std. dev. = 1.83 mm). Over 95% of choroidal melanomas are >5 mm in basal diameter and >1 mm in thickness. Choroidal nevi, which have a cumulative lifetime incidence of approximately 6.5% of persons, are at least 130 times as common as choroidal melanomas, which have a cumulative lifetime incidence of approximately 1 in 2000 persons. In spite of the dramatically different frequency distributions of choroidal nevi and choroidal melanomas, the markedly greater cumulative lifetime incidence of choroidal nevi results in considerable overlap between larger nevi and smaller melanomas.
Attempts to classify melanocytic choroidal tumors clinically as benign nevi versus malignant melanomas on the basis of tumor size are likely to result in multiple misclassifications, especially of lesions having a maximal basal diameter >5 mm but <10 mm and a thickness >2 mm but less than 3.5 mm.
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