Original description of the chicken sarcoma (Rous sarcoma). Rous demonstrated that sarcomatous tumors in hens could be transmitted to normal hens by the injection of cell-free filtrates (virus) of the original tumor. The Rous Sarcoma Virus was the first oncovirus discovered.

Fifty-five years later, in 1966 Rous shared the Nobel Prize in Physiology or Medicine with Charles Huggins "for his discovery of tumor-inducing viruses and his work on cancer."