Tumors formed by human rhabdomyosarcoma cells in chorioallantoic membrane of embryonated hens' eggs

Abstract Cultured human rhabdomyosarcoma (RD) cells were seeded on the chorioallantoic membrane of embryonated hens' eggs at the 10th to 12th day of incubation. When the membranes were harvested after 18 to 19 days' incubation, tumors had formed in eggs seeded with 5 × 105 to 10 × 106 RD cells. The microscopic appearance of the tumors was similar to that of the rhabdomyosarcoma of the patient from whom the cell line was derived. In contrast to cell lines derived from RD cell tumors which formed in a cat or an NIH‐Swiss mouse and released the endogenous viruses of the cat and mouse, respectively, none of 36 cell lines derived from 13 tumors formed on the chorioallantoic membrane of hens' eggs released a type‐C virus and none contained the avian virus group‐specific antigen.