TETRASOMY-8 AS A CLONAL ANOMALY IN MYELOID NEOPLASIAS

Tetrasomy of chromosome 8 as a sole anomaly is apparently extremely ra re in acute nonlymphocytic leukemia (ANLL): Only two cases have been r eported, one of ANLL (M5b) with this karyotype. Very recently, another case was reported of a myelodysplastic syndrome (MDS) with isolated t etrasomy 8. We report tetrasomy 8 in four cases of ANLL, two of them w ith M5 and one with M1 subtype. Although in the latter case, tetrasomy 8 was evident in all karyotypes analyzed, in all other cases it const ituted a subpopulation of cells other than those with trisomy 8 and th ose with a normal karyotype (in only one case another change was evide nt in the karyotype). Using fluorescence in situ hybridization (FISH), the proportion of tetrasomic cells was determined in interphase nucle i. By this technique, small cell populations (3-9%) were detected in t hree additional trisomy cases. An additional ''control'' group of five trisomy cases did not show a significant population of tetrasomic int erphase nuclei. The data show that tetrasomy 8, if present as a sole a nomaly in ANLL, may play a rather specific role for the subtype, and p robably for the progression of myeloid neoplasia as well.