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840 CHROMOSOME ABNORMALITIES IN OSTEOSARCOMA DEVELOPING THIRTEEN YEARS AFTER TREATMENT FOR RETINOBLASTOMA

There is a high incidence of second malignancies, especially osteosarcoma, in survivors of hereditary retinoblastoma. The retinoblastoma “gene” which has been assigned to chromosome region 13ql4 has been proposed to be a more generalized cancer gene and the link between these two diverse tumors. Non-random abnormalities, primarily deletions, have been seen in the 13ql4 region in a significant number of retinoblastoma tumor cells and is felt to be the second event. Osteosarcoma tumor cells of a right temporal bone from a 13-year-old female who had received radiation therapy (5000 R) at age 12 weeks for bilateral retinoblastoma was grown in culture and analyzed. The patient had received high-dose methotrexate 2 months before the tumor resection. Cytogenetic analysis of primary cultures show 15% with abnormalities of the #13 chromosome with 5/15 with a deletion in the 13ql4 region. Other clonal abnormalities were also noted. Simultaneous examination of peripheral lymphocytes and skin fibroblasts show 46XX normal female chromosome complement. This patient provides evidence for a common chromosomal connection between these two tumors.