CYTOGENETIC CLONALITY ANALYSIS IN MYELODYSPLASTIC SYNDROME - MONOSOMY-7 CAN BE DEMONSTRATED IN THE MYELOID AND IN THE LYMPHOID LINEAGE

Bone marrow and blood from three patients with myelodysplastic syndrom e (MDS) and monosomy 7 were studied for cell lineage involvement of th e chromosomal abnormality. Cytogenetic involvement of the myeloid and eryrthroid cell lineages in MDS with monosomy 7 has been shown before. Lymphoid subpopulations have also been investigated but generally wit h negative results. A combined technique of May-Grunwald-Giemsa (MGG) for cell cytology and interphase fluorescence in situ hybridization (F ISH) using a chromosome 7 specific DNA probe was applied. Further, imm unophenotype and genotype of the cells were simultaneously examined wi th alkaline phosphatase anti-alkaline phosphatase (APAAP) immunostaini ng and FISH. The monosomy 7 was found in the blasts and in all or in s ubpopulations of myeloid and erythroid cells. T cells (CD3(+), CD5(+)) did not appear to be involved. B cells (CD19(+), CD22(+)) showed a no rmal distribution of FISH spots in two patients. In one patient howeve r the loss of a chromosome 7 was found in approximately 70% of the cel ls positive for B cell markers including CD79a. The results of this st udy show that in some cases MDS is a disease arising in a progenitor c ell with repopulative abilities restricted to myelopoiesis and erythro poiesis. In other cases, the pluripotent progenitor cells in MDS may s how the capacities to differentiate into B lineage lymphoid cells, as well as suggesting that in those instances MDS represents a condition of more primitive transformed hematopoietic ancestor cells.