Uterine artery embolization of leiomyomas with trisacryl gelatin microspheres (TGM): pathologic features and comparison with polyvinyl alcohol emboli.

Abstract

In recent years, uterine artery embolization (UAE) has gained popularity as an alternative to surgery for the treatment of symptomatic uterine leiomyomas. Polyvinyl alcohol (PVA) particles have been the principal agent used for UAE. Recently, trisacryl gelatin microspheres (TGM) have been advocated as a preferable occlusive material for UAE. It is the first embolic agent to be cleared specifically by the United States Food and Drug Administration for this use. To date, information on the tissue effects, distribution, and morphology of UAE with TGM in resected human organs is very limited. Herein, we document the pathologic findings in a 46-year-old woman who underwent hysterectomy and bilateral salpingo-oophorectomy and omentectomy for metastatic colonic adenocarcinoma 19 months after UAE with TGM (microsphere size = 500-700 micron) for uterine leiomyomas. Histologically, a submucosal leiomyoma and an intramural uterine leiomyoma showed massive coagulative necrosis of the infarct-type with a peripheral zone of hyalinized fibrous tissue. Aggregates of TGM were within the necrotic leiomyomas and throughout the myometrium. Non-targeted extrauterine sites also contained TGM, including the paracervical soft tissue and the mesosalpinx as well as the ovaries and omentum where they were adjacent to metastatic colonic carcinoma. Other than the myomas, none of the embolized organs showed ischemic necrosis. Although some TGM were intravascular, most were extravascular. Typically, the microspheres were adjacent to muscular arteries from which they appeared to have been extruded following localized dissolution of the arterial wall. A thin rim of foreign body-type giant cells and mononuclear macrophages surrounded many of the TGM and focally involved the arterial wall. No vascular thrombosis was seen. TGM are believed to have advantages over PVA emboli for UAE. Hence, additional examples of surgical specimens following treatment of leiomyomas with TGM can be expected. Pathologists should be aware of the morphology of TGM in resected genital tract tissues. Although TGM are easily distinguished from embolic PVA particles, they may be mistaken for PVA microspheres if not carefully studied. Elastic stains are useful in the differential diagnosis of embolic agents.