For some tumor types, the germline predisposition was readily noted in this cohort, for example 10 of the 14 affected relatives who had a proband with retinoblastoma were diagnosed with the same cancer, an unsurprising finding given that germline RB1 mutations account for a significant proportion of retinoblastoma are highly penetrant and those tumors tend to be diagnosed young. This evidence concerns the gene RB1 and retinoblastoma.