Chromosomal translocations affecting 12q14-15 but not deletions of the long arm of chromosome 7 associated with a growth advantage of uterine smooth muscle cells

Cytogenetically, uterine leiomyomata are the best investigated human tumour s. The most frequent clonal abnormalities are structural rearrangements inv olving 12q14-15 and deletions of part of the long arm of chromosome 7. The present study investigated a possible growth advantage conferred by these a bnormalities, when compared with myomata having an apparently normal karyot ype. A total of 155 myomata were included in the study. All samples were ob tained after hysterectomy enabling karyotype analysis of all detectable tum ours. Myomata with clonal chromosome abnormalities were significantly large r than those with a normal karyotype (6.8 +/- 5.3 versus 3.4 +/- 2.1 cm; P < 0.001). However, when differentiating between the two main aberrations, t his was found to be true for the myomata with 12q14-15 changes affecting th e high mobility group protein IC (HMGIC) gene (8.9 +/- 5.6 cm), but not for the group of tumours characterized by deletions of chromosome 7 (3.5 +/- 2 .0 cm). The results are compatible with the hypothesis that myomata develop due to an unknown event, whereas the chromosomal abnormalities act as seco ndary changes, with those affecting the HMGIC gene increasing the growth po tential of the corresponding tumours.