Certain chromosome abnormalities have been detected in routine cytogenetic studies of patients with hematologic disorders. This article is a cytogenetic and clinical review of 28 structural and 15 numeric chromosome abnormalities. As a group, the structural abnormalities involved 40 different chromosome breakpoints and included 13 types of translocations, 8 deletions, 3 isochromosomes, 3 inversions, and 1 duplication. The numeric abnormalities included 4 types of monosomy, 10 trisomies, and a near-haploid category. We determined the relative frequency for each of these anomalies in our practice by reviewing the results of 1,228 consecutive specimens studied between 1979 and 1984 in which a chromosomally abnormal clone was found; 61% of these specimens had one or more of the selected anomalies. The three most common translocations were 9;22 translocations (378 specimens), 8;21 translocations (15 specimens), and unbalanced abnormalities derived from 1;7 translocations (13 specimens). The two most common deletions were those involving the long arm of chromosomes 5 (101 specimens) and 20 (65 specimens). The most common isochromosome was i(17q) (33 specimens). The two most common types of monosomy were loss of a Y chromosome (118 specimens) and monosomy 7 (97 specimens). The three most common trisomies were +8 (161 specimens), +21 (53 specimens), and +19 (31 specimens). Each of the 43 anomalies was observed in patients with different types of hematologic disorders, but in most cases one kind of neoplasm usually predominated.
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