[Is leukemic transformation of donor cells possible?]

To genotype tumor cells in the recurrence of leukemia after allogenic transplantation of bone marrow (TBM).

Standard cytogenetics and fluorescent hybridization in situ (FISH) with a probe to the centrometic sites of X/Y chromosomes were used in examination of 2 patients with acute promyelocytic and acute non-differentiated leukemia after allogenic TBM from donors of the opposite gender. Bone marrow was studied 1, 2, 3, 6, 9, 12, 15, 17, 18 months after the transplantation.

One of the patient in leukemia recurrence there were 72% cells with one X chromosome with unknown origin. 28% donor cells were with genotype XX. The primary archival cytological sample of the recipient's bone marrow 68% cells did not contain Y chromosome. Thus, the clone with Y loss is the recipient's clone and leukemia after transplantation developed from the recipient's cells. The other patient had only 8% dividing cells with her karyotype XX with translocation t(10;11) while 92% metaphases were donor's ones; the interphase cells ratio was 75% of host cells and 25% donor cells. This confirms leukemia origin from the recipient's cells.

High sensitive quantitative method FISH indicates a true correlation between the host and donor cells and is a method of choice for genotyping leukemic cells in recurrence after transplantation of bone marrow. While standard caryotyping depends on mytotic activity of donor and host cell populations, use of only one cytogenetic test for determination of leukemia origin after TBM may provoke diagnostic errors.