Is trisomy 4 a secondary chromosomal abnormality in acute myeloblastic leukemia?

Cytogenetic studies were carried out in a patient with acute monocytic leukemia (AML-M5) at diagnosis and in relapse. While no chromosome abnormality was detected initially, isolated trisomy 4 was found in relapse. The primary or secondary nature of trisomy 4 as the sole abnormality in AML is discussed.