Natural Size Development of Myomata - Ultrasound Observational Study of 55 Premenopausal Patients

Growth of surgically confirmed leiomyomas in postmenopausal women: analysis of the influencing factors

OBJECTIVES

The aim of this study was to examine the growth of uterine leiomyomas in postmenopausal women and evaluate the influencing factors associated with fibroid growth.

METHODS

We retrospectively analyzed the medical records of postmenopausal women with fibroids between 2015 and 2020. All women received at least 2 transvaginal ultrasound examinations within a 6-month interval. All fibroids were verified via surgery. The postoperative pathology of all tumors was uterine fibroid. We calculated the fibroid volume using the ellipsoid volume formula and evaluated the growth rate of fibroids within 6 months simultaneously. Univariable analysis and a linear mixed-effects model were used to assess the factors influencing fibroid growth.

RESULTS

A total of 102 postmenopausal women with a total of 132 fibroids were assessed. The median growth rate of surgically confirmed fibroids in postmenopausal women was 12.9% every 6 months (from -61.4% to 184.1%). Obesity was associated with fibroid growth (P < 0.05). Notably, the estimated growth rates of fibroids in obese and overweight women were 26.6% (95% confidence interval [CI]: 2.3-50.9) and 15.9% (95% CI: 0.4-31.4) higher than those in women of normal weight, respectively. The growth of fibroids varied by the initial tumor size (P < 0.05). The estimated growth rate of larger fibroids (≥5.0 cm diameter) was reduced 30.0% (95% CI: -52.4 to -7.5) compared with that of small fibroids (<3.0 cm diameter).

CONCLUSIONS

Uterine fibroids continually grow in some postmenopausal women. Obesity and small fibroids (<3.0 cm diameter) may contribute to higher growth rates of fibroids.

Uterine fibroid incidence and growth in an ultrasound-based, prospective study of young African Americans

BACKGROUND

Uterine fibroids are common. Symptoms are debilitating for many, leading to high medical and societal costs. Indirect data suggest that compared with white women, African Americans develop fibroids at least 10 years earlier on average, and their higher health burden has been well documented.

OBJECTIVE

The objective of the study was to directly measure fibroid incidence and growth in a large, community-based cohort of young African-American women.

STUDY DESIGN

This observational, community-based, prospective study enrolled 1693 African-American women, aged 23-35 years with no prior diagnosis of fibroids. Standardized transvaginal ultrasound examinations at enrollment and after approximately 18 months were conducted to identify and measure fibroids ≥0.5 cm in diameter. Fibroid growth (change in natural log volume per 18 months) was analyzed with mixed-model regression (n = 344 fibroids from 251 women whose baseline ultrasound revealed already existing fibroids).

RESULTS

Among the 1123 fibroid-free women with follow-up data (88% were followed up), incidence was 9.4% (95% confidence interval, 7.7-11.2) and increased with age (P_trend < .0001), from 6% (confidence interval, 3-9) for 23-25 year olds to 13% (confidence interval, 9-17) for 32-35 year olds. The chance of any new fibroid development was greater than twice as high for women with existing fibroids compared with women who were fibroid free at baseline (age-adjusted relative risk = 2.3 (confidence interval, 1.7-3.0). The uterine position of most incident fibroids (60%) was intramural corpus. Average fibroid growth was 89% per 18 months (confidence interval, 74-104%) but varied by baseline fibroid size (P < .0001). Fibroids ≥2 cm in diameter had average growth rates well under 100%. In contrast, small fibroids (<1 cm diameter) had an average growth rate of nearly 200% (188%, confidence interval, 145-238%). However, these small fibroids also had a high estimated rate of disappearance (23%).

CONCLUSION

This is the first study to directly measure age-specific fibroid incidence with a standardized ultrasound protocol and to measure fibroid growth in a large community-based sample. Findings indicate that very small fibroids are very dynamic in their growth, with rapid growth, but a high chance of loss. Larger fibroids grow more slowly. For example, a 2-cm fibroid is likely to take 4-5 years to double its diameter. Detailed data on fibroid incidence confirm an early onset in African-American women.

Differences in the cellular composition of small versus large uterine fibroids

Uterine fibroids are clonally derived from a single cell; however, despite being monoclonal, the cellular phenotypes that make up uterine fibroids are heterogeneous consisting of predominantly smooth muscle cells (SMC) and fibroblasts. This raises the question as to when clonal cell differentiation occurs during fibroid development, and does this information provide clues about possible mechanisms regulating the growth process that leads to fibroids of symptom-causing size? This study investigated the differences in the cellular composition of fibroids by immunohistochemistry (IHC). A tissue microarray (n = 21 hysterectomy cases) was used for the investigation of large uterine fibroids and normal myometrium. An investigation of small fibroids (≤ 5mm) used a separate group of samples (n = 7 hysterectomy cases, total of n = 17 fibroids). A panel of cell phenotypic markers was selected based on our previous in situ investigations and included aldehyde dehydrogenase 1 (ALDH1A1) and vimentin for different fibroblast sub-populations, smooth muscle actin (SMA) as a marker for SMCs, CD31 for endothelial cells and CD45 for leucocytes. Proliferating cell nuclear antigen (PCNA) was also studied to identify proliferating cells. The cellular composition of small fibroids differs significantly from large fibroids. Small fibroids are more cellular (increased cells/mm(2)) than large fibroids, have more blood vessels and also have a higher ratio of SMC to fibroblasts than large fibroids. Large fibroids have more cell proliferation (measured by PCNA) and fewer leucocytes (measured by CD45) than adjacent myometrium, whereas small fibroids are less proliferative and have similar number of leucocytes to myometrium. Different cellular composition between fibroids of different sizes may provide important clues as to the mechanisms that drive fibroid growth.