Cytogenetic clonality analysis in monosomy 7 associated with juvenile myelomonocytic leukemia: clonality in B and NK cells, but not in T cells

It remains unclear which lymphoid lineages are involved in juvenile myelomonocytic leukemia (JMML). We report a JMML patient who acquired monosomy 7 after intensive chemotherapy. In this case, the expression of monosomy 7 was analyzed in T, B and natural killer (NK) cells highly purified from peripheral blood mononuclear cells of the patient. The fluorescence in situ hybridization method revealed the expression of monosomy 7 in B cells, but not T cells. Half of the NK cells expressed monosomy 7; when NK cells were divided into CD2 − and CD2 + populations, this abnormality was positive in 91.1% of CD2 − NK cells but in only 14.7% of CD2 + NK cells. These results suggest that, in this JMML patient who acquired monosomy 7 after intensive chemotherapy, B cells and half of NK cells, but not T cells, have monosomy 7.