Type I MOZ/CBP (MYST3/CREBBP) is the most common chimeric transcript in acute myeloid leukemia with t(8;16)(p11;p13) translocation.

The t(8;16)(p11;p13) fuses the MOZ (MYST3) gene at 8p11 with CBP (CREBBP) at 16p13 and is associated with an infrequent but well-defined type of acute myeloid leukemia (AML) that has unique morphocytochemical findings (monocytoid blast morphology with erythrophagocytosis and simultaneously positive for myeloperoxidase and nonspecific esterases). RT-PCR amplification of MOZ/CBP (MYST3/CREBBP) chimera has proved difficult, with four different transcripts found in four reported cases. We studied 7 AML-t(8;16) patients, 5 with cytogenetically demonstrated t(8;16) and 2 with similar morphocytochemical and immunophenotypical characteristics. Clinically, 3 cases presented as therapy-related leukemia. Extramedullar involvement was observed at presentation in 2 patients and coagulopathy in 4. The clinicobiological findings confirmed the distinctiveness of this entity. Of note is the erythrophagocytosis in 5 of 7 cases and the immunological negativity for CD34 and CD117 and positivity for CD56. Using a new RT-PCR strategy, we were able to amplify a specific band of 212 bp in six cases in which sequence analysis confirmed the presence of the previously described MOZ/CBP fusion transcript type I. This is the largest molecularly studied AML-t(8;16) series, which demonstrates that MOZ/CBP breakpoints are usually clustered in intron 16 of MOZ and intron 2 of CBP. The newly designed single-round PCR provides a simple tool for the molecular confirmation of MOZ/CBP rearrangement.