Histogenesis of Malignant Melanomas of the Uvea

Nevus-like structures were observed at the base of experimental choroidal tumors. These neoplasms were obtained by injecting Greene transmissible hamster melanoma cells into the choroid of Syrian hamsters and murine neuroblastoma cells into the choroid of A/J strain mice. Cells from both tumors, when injected intraocularly or systemically, give rise to lesions composed predominantly of epithelioid or round cells. The choroidal tumors in both species, however, generally showed a zone of flattened cells adjacent to the sclera, composed of relatively benign-appearing, smaller, and more delicate cells—and in the case of the melanoma, usually more densely pigmented cells—than the main portion of the tumor. The cells in this area appeared similar to the "nevus cells" that have long been described beneath and adjacent to primary malignant melanomas of the uvea.