Molecular cytogenetic studies characterize a near-triploid complex karyotype in a child with acute lymphoblastic leukemia.

High hyperdiploidy with modal chromosome numbers between 50 and 65 is common in childhood acute lymphoblastic leukemia (ALL), occurring in 25-30% of the cases. This chromosomal constitution is associated with a very good prognosis. By contrast, near triploidy and tetraploidy are found in <1% of childhood ALL. Given the sparseness of this group, the associated chromosomal abnormalities and their prognostic implications have not yet been studied in detail. Here, we describe clinical and molecular cytogenetic findings in a child with ALL who had a near-triploid complex karyotype, with loss and gain of chromosomes, including extra copies of the same derivative chromosomes. These findings suggest a random nondisjunction mechanism for near triploidy in the present case.