Analysis of the AML-1-TEL translocation in a bone marrow smear 8 years and 9 months before diagnosis of leukemia. The 411-bp heminested AML-1-TEL PCR product was amplified from 10 ng of diagnostic DNA from T-2850 (T-2850, diag.) and 4 ng of DNA isolated from a stored bone marrow smear prepared 8 and a half years before diagnosis (T-2850, slide). Lanes containing 50 ng of DNA from normal controls (CON-1, CON-2) were negative.