CORRELATION BETWEEN CELL MORPHOLOGY AND EXPRESSION OF THE AML1 ETO CHIMERIC TRANSCRIPT IN PATIENTS WITH ACUTE MYELOID-LEUKEMIA WITHOUT THE T(821)/

The 8;21 chromosomal translocation involves the AML1 gene on chromosom e 21 and the ETO gene on chromosome 8 and results in the transcription of a chimeric message. This translocation is most often associated wi th acute myelogenous leukemia with maturation (AML-M2). The leukemic c ells of patients carrying t(8;21) often exhibit several characteristic morphologic features. We identified four cases in which the morpholog y led us to suspect a t(8;21), but in which this translocation was not observed by cytogenetic analysis. In two of the four cases, an AML1/E TO chimeric fragment was detected by reverse transcription and polymer ase chain reaction (RI-PCR), and its sequence was found to be identica l to that from patients with a cytogenetically proved t(8;21). Marrow specimens of the four patients lacking the t(8;21) cytogenetically wer e reviewed retrospectively with regard to seven morphologic features c ommonly reported to be associated with this translocation, and the res ults were compared to 13 morphologic controls with the t(8;21). Althou gh none of the 13 controls had all of the characteristic morphologic f eatures, all had at least six, as did the two t(8;21)-negative but RT- PCR-positive patients. The two patients who lacked the t(8;21) and who were RT-PCR-negative showed only three and four of these morphologic features, respectively. Both of the RT-PCR-positive patients had delet ions of the long arm of chromosome 9, a common change associated with a t(8;21), supporting our assessment of these patients as having a cyt ogenetically undetected t(8;21).