Histogenesis of malignant melanomas of the uvea.II. Relationship of uveal nevi to malignant melanomas

Many theories concerning the histogenesis of uveal melanomas have been advanced. While much clinical as well as histopathologic evidence is available to support the belief that most malignant melanomas of the iris have their origin in pre-existing nevi, the histogenesis of melanomas of the choroid and ciliary body is much more controversial. A histopathologic study of 100 consecutive malignant melanomas of the choroid and ciliary body was undertaken in an effort to ascertain the frequency with which benign-appearing cells (nevus cells) might be found within or along the edges of the tumors. Such cells, cytologically identical with the cells constituting nevi of the uveal tract, were found in considerable numbers in 73 of the 100 melanomas. The authors conclude that most malignant melanomas, perhaps all such neoplasms, have their origin in pre-existing nevi.