We, therefore, extended the study to accurately and reproducibly determine TEL-AML1 mRNA levels in 47 additional patients with t(12;21).     ///    The observed variation in TEL-AML1 transcript levels is of interest because it could reflect biological and/or clinical heterogeneity in the behavior of these leukemias..     ///    "During the course of these studies, we found marked variations in the levels of the TEL-AML1 transcripts in individual patients. "    ///    "The results indicated that the level of expression of TEL-AML1 varied among individual patients, and it was independent of the WBC count. "    ///    "We validated this method with 92 primary ALLs and identified 4 E2A-PBX1, 4 mBCR-ABL and 10 TEL-AML1. "