Multicystic Benign Cystic Mesothelioma Presenting as a Pelvic Mass

Background. Benign cystic mesothelioma (BCM) is a rare tumor that arises from the abdominal peritoneum with a predilection to the pelvic peritoneum. For this reason, it can often mimic gynecologic malignancies. Case. A 47-year-old perimenopausal female presented reporting several weeks of abdominal distention associated with abdominal tenderness and constipation. Computed tomography revealed a 24？cm multiloculated pelvic mass, and tumor markers were notable for an elevated CA-125. The patient was taken to the operating room for an exploratory laparotomy, total abdominal hysterectomy, bilateral salpingoophorectomy, and removal of pelvic mass. Final pathologic evaluation revealed a benign cystic mesothelioma. Conclusion. Classically these tumors present as large multicystic masses with thin-walled septations and on preoperative evaluation BCM can mimic many different disease entities including ovarian malignancies and cystic lymphangioma. Often diagnosis can only be made at time of surgery. 1. Introduction Differential diagnosis of a pelvic mass in a reproductive age female can be difficult and often requires surgical exploration and pathologic diagnosis. Benign cystic mesothelioma is a rare intra-abdominal tumor that can present as a large multicystic mass arising from the pelvis. To date, approximately 140 cases have been described in the literature, most occurring in reproductive aged women. The pathogenesis of this disease remains unclear, although many agree that it is likely the result of a chronic inflammatory process as in the case of endometriosis. BCM is generally considered a benign process; however given the high rate of recurrence and possible malignant transformation, close follow-up is important. 2. Case Report Written informed consent for publication was first obtained from the patient as outlined by the Institutional Review Board. A 47-year-old perimenopausal female presented to her gynecologist’s office complaining of worsening abdominal distention, abdominal tenderness, and constipation for over 3 weeks. Past medical and surgical history was significant for hypothyroidism, latent tuberculosis, and cesarean section with bilateral tubal ligation. She had no smoking history and family medical history was noncontributory. On physical exam, vital signs were within normal limits and the abdomen was distended and diffusely tender. Pelvic exam was significant for a 30？cm adnexal mass. The uterus was small and difficult to palpate secondary to the large adnexal mass. The remainder of the physical exam and review of systems were otherwise