(1) There is a spectrum of imaging appearances, with heterogeneity caused by bleeding, infarction and fibrous degeneration
. MRI shows a T1 isointense, T2 isointense-to-hypointense mass with cystic spaces (Figure 16A).
Recent evidence suggests that fibrous degeneration (hyalinization) may play a major role[3,6] The data suggest that fibrous degeneration in small myomas ([is less than] 1 cm) does not reflect outgrowth of vascular supply, but rather represents an in vivo correlate of the senescence that occurs in myoma tissue maintained in vitro.[6,7] The purpose of the present study was to use morphometry to compare myoma cell size in a series of sizematched small uterine leiomyomas from age-matched premenopausal and postmenopausal women.
The tumors were also matched with regard to intramural location and matched within 1 grade in degree of fibrous degeneration ([+ or -], 1-10%; 1+, 11-25%; 2+, 26-50%; 3+, 51-75%; and 4+, [is greater than] 75%). We also reviewed several hundred routinely processed hysterectomy specimens, and found additional small myomas that qualified as members of 8 additional matched pairs.
Any dilation of the vessels exaggerated the proportion of stroma, even in the absence of discernible fibrous degeneration. Artefactual holes in the sections also exaggerated the percentage of stroma, but these holes were generally infrequent and inconsequential.
The 9 myomas graded as having 1+ fibrous degeneration had an average relative myoma cell area of 79%.
It has been reported that fibrous degeneration, apparently reflecting senescent dropout of myoma cells, may be a major factor contributing to postmenopausal shrinkage of small uterine myomas. In that study, larger myomas ([is greater than] 1 cm) were excluded because their longer duration increased their window of vulnerability to possible variations in levels of hormones or growth factors, secondary to diseases and/or treatments.[9-13] Their larger size also increased the possibility that they may have undergone changes related to outgrowth of their blood supply.
However, almost all of patients were in the age range when postmenopausal fibrous degeneration is most prevalent, so it seems likely that most of the postmenopausal myomas had shrunk.