Different proliferative and apoptotic activity in peripheral versus central parts of human uterine leiomyomas.

OBJECTIVE

To determine whether there are differences in proliferative and apoptotic activity and in expression of sex steroid receptors between central and peripheral parts of human uterine leiomyomas in different menstrual cycle phases.

METHODS

Biopsy specimens of the myometrium and peripheral and central parts of uterine leiomyomas were obtained from 15 women in the proliferative phase and 8 women in the secretory phase. Mitotic cells were detected by immunohistochemical staining for Ki67. Apoptotic cells were detected by the TUNEL method. Mitotic and apoptotic indexes were calculated. Tissue levels of oestrogen and progesterone receptors were measured using a commercial monoclonal receptor enzyme immunoassay kit.

RESULTS

During the secretory phase the mitotic index was significantly higher in the peripheral than in the central parts of the leiomyomas. During the proliferative phase the apoptotic index was significantly higher in the peripheral compared with the central parts. These differences were not reflected by differences in receptor expression.

CONCLUSIONS

The results of this study suggest that the growth of a human uterine leiomyoma mainly occurs in the peripheral parts of the tumour, during the secretory phase of the menstrual cycle. The findings emphasise the importance of being consistent when taking samples for research work.