Relationship of myoma cell size and menopausal status in small uterine leiomyomas

Context.-Although myomas shrink after menopause, the cellular mechanism for this phenomenon has received little attention. It was recently demonstrate d that fibrous degeneration is significantly associated with postmenopausal status in both small and large myomas. Objective.-The purpose of the present study was to evaluate whether reducti on in myoma cell size is also associated with postmenopausal status in smal l myomas. Design.-Tumor size and patient age have also been related to fibrous degene ration in small (<1 cm) myomas. Therefore, in the present study, 10 pairs o f premenopausal and postmenopausal small myomas were matched within 3 years for patient age, within 1 mm for size, and within 1 grade for degree of fi brous degeneration. Most of the women were in their 50s, the decade during which postmenopausal fibrous degeneration in small myomas is most prevalent . Myoma cell size was derived by morphometric evaluation of relative myoma cell area (correcting for percentage of stroma, as measured by point counti ng) and by direct counting of the number of myoma cells per unit area in tr ichrome-stained sections. Results.-Small myomas from postmenopausal women had significantly (P < .05) smaller cell sizes than did size-matched myomas from age-matched premenopa usal women. Myoma cell sizes and nucleus-cell (N/C) ratios were highly vari able, especially in premenopausal myomas. Conclusions.-Reduction in myoma cell size is significantly associated with postmenopausal status in small uterine leiomyomas and may be an important m echanism for postmenopausal shrinkage of myomas. In addition, the high vari ability of myoma cell size and N/C ratio may further support the somatic mu tation theory (ie, the theory that diverse mutations may account not only f or variations in the growth potential of uterine myomas, but also for varia tions in their cellular details).