CHROMOSOME-7 BICLONALITY IN UTERINE LEIOMYOMA

Biclonal chromosome complements in uterine leiomyoma have been reported occasionally. These previous studies reported the presence of two unrelated clones containing mainly t(12;14) and del(7). We describe four cases of typical leiomyoma displaying two clones, both involving chromosome 7 but with a different deletion in each of the two clones. For two of the tumors, the biclonal origin is the only possible explanation; for the remaining two cases, the origin of the two deleted chromosomes 7 could also be explained by clonal evolution, since the more proximal deletion on chromosome 7 in one clone appears to-be subsequent to the deletion of the other clone. Even in these cases, however, the biclonal origin cannot be excluded completely. Despite the mechanism of origin, deletion of chromosome 7 is the most common cytogenetic abnormality in leiomyoma, indicating that loss of genetic material from the long arm of this chromosome is critical for tumor development.