A rare case of leiomyosarcoma originating from the left round ligament of the uterus

Headnote

Keywords: Round ligament, uterine leiomyosarcoma, premenopausal woman

[PP-097]

Introduction: Uterine leiomyosarcomas (LMS) are rare malignancies with a poor prognosis. The Incidence is reported to be 3-7/100,000 per year. Preoperative and intraoperative differentiation between LMS and large leiomyoma is always challenging. Therefore, LMS are often diagnosed during postoperative histologic evaluation of hysterectomy or myomectomy specimens. LMS of the round ligament of the uterus which can represent as an inguinal or pelvic mass is extremely rare. To our knowledge, there is only one case report of LMS arising from the round ligament available in the literature. Herein, we aimed to present the second case of LMS originating from the left round ligament of the uterus in a premenopausal woman initially misdiagnosed as an ovarian tumor. Case: A 43-year-old woman (gravida 4, parity 4) applied to our outpatient clinic with a complaint of abdominal pain and distension since 3 months. Her past medical and family histories were unremarkable. She was menstruating regularly. Pelvic examination disclosed a solid, immobile mass in the left adnexal localization, extending to over the umbilicus. On ultrasonographic examination, an anteverted uterus with an endometrium thickness of 8 mm and homogenous myometrium were observed. The ovaries could not be visualized, and the mass filling the left adnexal region and whole abdomen displaced the uterus to the right side. The round mass with heterogeneous internal echogenicity was measured at 19 cm diameter on the ultrasound scan. An amount of free fluid collection was also detected in the pouch of Douglas. Complete blood count values and other laboratory test results including tumor markers were unremarkable. Moreover, endometrial biopsy and Pap smear test results were also normal. An exploratory laparotomy was performed, and approximately 25 cm solid mass arising from the left round ligament was observed during the operation (Figure 1). The result of the intraoperative frozen section was reported as malignant. Therefore, the patient who does not desire fertility underwent complete surgical staging, including total abdominal hysterectomy, bilateral salpingoopherectomy, lymphadenectomy, appendectomy, and omentectomy. Her postoperative course was uneventful. On histologic examination, more than 3 mitotic figures were observed in the field at 40x magnification (Figure 2). Histopathology was reported as LMS.

Conclusion: LMS of the round ligament of the uterus are extremely rare malignancies. They may be present with a pelvic or inguinal (extra pelvic) mass depending on which part of the round ligament involved. LMS can also occur without any risk factors. However, a rapidly growing, large and solitary uterine mass may be a sign of uterine sarcoma, even though in women of reproductive age.