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 demonstrated 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 reduction in myoma cell size is also associated with postmenopausal status in small myomas. DESIGN: Tumor size and patient age have also been related to fibrous degeneration in small (<1 cm) myomas. Therefore, in the present study, 10 pairs of 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 fibrous 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 counting) and by direct counting of the number of myoma cells per unit area in trichrome-stained sections. RESULTS: Small myomas from postmenopausal women had significantly (P <.05) smaller cell sizes than did size-matched myomas from age-matched premenopausal women. Myoma cell sizes and nucleus-cell (N/C) ratios were highly variable, 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 mechanism for postmenopausal shrinkage of myomas. In addition, the high variability of myoma cell size and N/C ratio may further support the somatic mutation theory (ie, the theory that diverse mutations may account not only for variations in the growth potential of uterine myomas, but also for variations in their cellular details).