Ovarian Endometrioma with Osseous Metaplasia: A Case Report and Review of the Literature

Abstract Background: Osseous metaplasia of the nonteratomatous ovary is extremely rare. This condition has been reported in association with endometriosis and certain ovarian neoplasms. Case: A 35-year-old nulliparous patient presented with new-onset severe abdominal pain associated with abdominal fullness, nausea, and vomiting. She had a large, tender pelvic mass anterior to the cervix. Computed tomography showed a midline pelvic mass, measuring 13.1 × 12.3 × 9.3 cm, located anteriorly and superiorly to the uterine fundus, with partially calcified septations as well as an eccentric soft-tissue nodule The uterus was enlarged and lobulated, containing multiple fibroids. There was a complex cystic mass superior to the uterus producing low-level internal echoes and having a few septations with areas of calcification. The patient underwent an exploratory laparotomy during which the pelvic mass was identified as an endometrioma arising from the left ovary. The cyst was densely adherent to the superior aspect of a leiomyomatous uterus with a large fundal fibroid measuring ∼7 cm. Intraoperative pathologic evaluation revealed that this cyst was benign. Lysis of adhesions, followed by myomectomy, was performed, removing 19 fibroids weighing 235 g in aggregate. Results: The patient had an uncomplicated postoperative course and was referred for infertility evaluation. Pathologically, this lesion was consistent with an endometriotic cyst (endometrioma) with focal osseous metaplasia. Conclusions: It has been theorized that chronic inflammation might be a driving force in the formation of bone within these lesions.