Multicystic Mesothelioma of the PeritoneumLiem T. Bui-Mansfield1, Gina Kim-Ahn2, Larry K. O’Bryant3
During a pelvic examination, a 44-year-old woman was found to have an abdominal mass. Pelvic sonography revealed a complex multiseptate cystic mass (Fig. 1A). MR imaging showed a 15x9x7 cm mass arising from the uterine fundus; on T2-weighted images, the mass exhibited intermediate and high signal intensity. Fine septations were seen in the cystic component of the
mass (Fig. 1B). The patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy. The hysterectomy specimen showed an irregular multilocular cystic mass attached to the uterine fundus (Fig. 1C). Microscopic examinations found multiple mesothelium-lined cysts surrounded by a fibrovascular stroma with adenomatoid changes (Fig. 1D). The pathologic diagnosis was multicystic mesothelioma of the peritoneum.
Mesotheliomas are mesenchymal neoplasms originating in the serous lining of the pleura, pericardium, or peritoneum. Multicystic mesothelioma of the peritoneum is an intermediate form of mesothelioma: the severity of the disorder is greater than that of the localized, benign adenomatoid mesothelioma but is less than that of the highly lethal form of diffuse epithelial mesotheliomas [1]. Multicystic mesothelioma occurs predominantly (84% of cases) in young or middle-aged women (mean age, 37 years 10 months) [1, 2]. The tumor chiefly affects the pelvic peritoneum, particularly the uterus, cul-de-sac, bladder, and rectum, growing along the serosa as multiple translucent fluidfilled cysts. Multicystic mesothelioma is made up of mesothelium-lined cysts embedded in fibrovascular stroma. The mesothelial cells are typically flattened or cuboidal. In one third of patients, adenomatoid change or squamous metaplasia of the mesothelium is found [1]. Unlike the malignant form of mesothelioma, multicystic mesothelioma has no association with asbestos exposure [1]. The most common presenting symptoms are abdominal pain (46% of patients) and abdominal mass (29% of patients) [2]. In 18% of patients, the tumor is an incidental finding [2].
On sonography, multicystic mesothelioma appears as a multiseptate cystic mass [3]. Typically, CT reveals a well-defined, noncalcified multilocular cystic mass [2], although a case of calcification in a benign cystic peritoneal mesothelioma has been reported [4]. MR imaging shows well-defined lesions that are hypointense on T1-weighted images and have intermediate signal intensity on T2-weighted images, isointense to urine. This finding correlates with the clear watery fluid seen at gross pathologic examination [2].
Differential diagnoses include lymphangioma, endometriosis, ovarian cystadenoma or cystadenocarcinoma, teratoma, pseudomyxoma peritonei, necrotic leiomyoma or leiomyosarcoma, and epithelial inclusion cysts [1, 2]. Because of the rarity of multicystic mesothelioma, a correct preoperative diagnosis is almost never rendered [1]. Multicystic mesothelioma is not chemo- or radiosensitive. No correlation exists between the extent of the tumor and the patient’s survival. Treatment for localized lesions is total surgical excision, and for more extensive lesions, debulking procedures are performed.
