Tetrasomy 8 as a clonal anomaly in myeloid neoplasias.

Tetrasomy of chromosome 8 as a sole anomaly is apparently extremely rare in acute non-lymphocytic leukemia (ANLL): Only two cases have been reported, one of ANLL (M5b) with this karyotype. Very recently, another case was reported of a myelodysplastic syndrome (MDS) with isolated tetrasomy 8. We report tetrasomy 8 in four cases of ANLL, two of them with M5 and one with M1 subtype. Although in the latter case, tetrasomy 8 was evident in all karyotypes analyzed, in all other cases it constituted a subpopulation of cells other than those with trisomy 8 and those with a normal karyotype (in only one case another change was evident in the karyotype). Using fluorescence in situ hybridization (FISH), the proportion of tetrasomic cells was determined in interphase nuclei. By this technique, small cell populations (3-9%) were detected in three additional trisomy cases. An additional "control" group of five trisomy cases did not show a significant population of tetrasomic interphase nuclei. The data show that tetrasomy 8, if present as a sole anomaly in ANLL, may play a rather specific role for the subtype, and probably for the progression of myeloid neoplasia as well.