Excision of benign multicystic peritoneal mesothelioma and deep infiltrating endometriosis with bowel involvement – A case report

Benign multicystic peritoneal mesothelioma (BMPM) is a rare peritoneal tumour. Treatment involves complete surgical resection, although recurrence rates are high. Notably, there are 7 documented cases of BMPM coexisting with endometriosis on histology and in the case reported here it was associated with deep infiltrating endometriosis. Examination of the 26-year-old nulliparous woman with deep dyspareunia, dyschezia and occasional rectal bleeding revealed restricted uterine mobility and a rectovaginal nodule.

Magnetic resonance imaging (MRI) showed multiple clear cystic structures in the pelvis of unknown aetiology. Following discussion by a multidisciplinary team, a diagnostic laparoscopy was performed. Intraoperatively, bilateral endometriomas were identified, along with multiple fluid-filled cystic structures in the pelvis and on the anterior abdominal wall. An adhesiolysis and drainage of endometriomas was performed and the cystic structures were sent for histology.

Histopathology confirmed BMPM, positive for AE1/3 and calretinin. The patient was referred to a mesothelioma malignancy institute and advised to undergo definitive surgery by the local endometriosis team. A joint surgical procedure with a colorectal team involved laparoscopic excision of peritoneal cysts, cystectomy for bilateral endometriomas, and excision of deep infiltrating endometriosis with bowel shaving. Histopathology revealed benign mesothelial cysts with foci of endometriosis.

The patient had an uncomplicated recovery and is planned for long-term follow-up with the mesothelioma malignancy institute due to the high recurrence rate (up to 50 %). This case report suggests a definitive role of this two-stage procedure in patients with this diagnostic complexity and emphasises the role of multidisciplinary management.