Retinoblastoma Xenograft (IMAGE) Howard Hughes Medical Institute Caption Retinoblastoma, a rare form of eye cancer, usually develops in early childhood. Human tumor cells implanted and grown in mice could offer researchers a new way to study the cancer. A stained sample of one such tumor, or orthotopic xenograft, is shown. Credit Michael Clay, MD Usage Restrictions Must use with credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.