Advantages of Ulipristal Acetate for the Preoperative Treatment of Hypoechoic Cellular Leiomyomas

Rationale why study should be conducted: Leiomyomas are the most common benign neoplasm in women; it has been estimated that these tumors occur in at least 25% of all women, which is probably an underestimation, because this figure is based on a select population. They are histologically composed by smooth muscle cells with bland, uniform, cigar-shaped nuclei that are arranged in interlacing bundles, showing little or no mitotic activity. Cellular leiomyomas (CLs) are described as leiomyomas that are significantly more cellular than the surrounding myometrium, often with crowding and overlapping of nuclei.

The presenting symptoms do not differ from those of patients with typical leiomyomas. On gross examination, CLs are more often soft and appear more tan or yellow and less circumscribed than the usual leiomyomas.

Pre-operatively, anyway, CLs can be recognized at ultrasound evaluation because they appear as hypoechoic uterine lesions. It has been demonstrated that patients with hypoechoic myoma have a significantly longer surgery time after treatment with a GnRH analog than for the rest of the pretreated fibroids or the untreated patients with hypoechoic myomas. Considering the predominant relevance of the traction maneuvers in laparoscopic myomectomy, the difficulty in adequately grasping the tumor is the key element in the longer operative time. The greater softening of the fibroid tissue is probably related to degenerative changes induced by the GnRH-analog pretreatment, particularly in those fibroids without an adequate fibrous "skeleton" and thus with the appearance as hypoechoic at the admission ultrasonography. From a pathologic point of view, these fibroids, when pretreated, showed a predominance of areas of coagulative necrosis and mixoid degeneration, causing longer operative time and showing unequivocally the negative effect of preoperative GnRH analog treatment for these kinds of uterine fibroids.

At the same time, hypoechoic CLs should be more responsive to ulipristal acetate treatment than common leiomyomas, given its antiproliferative activity in cultured leiomyoma cells.

The antiproliferative ulipristal effect, moreover, induces a condition of apoptotic necrosis that, compared to GnRH-a myxoid necrosis, probably allows an easier surgical enucleation of the tumor.