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.
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%).
Any dilation of the vessels exaggerated the proportion of stroma, even in the absence of discernible fibrous degeneration.
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.
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.
Our measurements tend to validate the subjective grading of fibrous degeneration reported previously.
Both the senescence hypothesis that we endorse to explain fibrous degeneration in small myomas and our overall findings in premenopausal and postmenopausal myomas suggested that cells in the fibrotic zone would be smaller than those in the cellular zone.