Laparoscopic diagnosis and treatment of pelvic benign multicystic mesothelioma associated with high CA19.9 serum concentration

We report a case of benign multicystic mesothelioma in a 20-year-old woman referred because of amenorrhea. She underwent pelvic transabdominal ultrasound, which disclosed a micropolycystic appearance of the ovaries and a fluid collection in the pouch of Douglas. Tumor serum markers revealed an increase in CA19.9. Abdominal and pelvic computed tomography scans confirmed the presence of ascites. Laparoscopy disclosed small, thin-walled, translucent cysts in the Douglas cavity. The cysts were free-floating in a yellowish, sticky, gelatinous material. Microscopically, cystic lesions showed mesothelium-lined cystic spaces surrounded by a delicate thin fibrovascular wall. With immunohistochemistry, the tumor cells were strongly positive for cytokeratin and calretinin. These aspects were suggestive of benign multicystic mesothelioma. Electron microscopy confirmed the mesothelial nature of this tumor. Serial evaluation of the CA19.9 concentration showed a progressive decrease in the serum marker in the normal range. The patient is now well and symptom-free with no recurrence 24 months after surgery. The association between benign multicystic mesothelioma and increased CA19.9 serum concentration has been described only once, in a man. To our knowledge, this is the second case of benign multicystic mesothelioma associated with increased CA19.9 serum concentration and the first diagnosed in a woman. In the present case, a minimally invasive laparoscopic approach enabled not only histologic diagnosis of benign multicystic mesothelioma but also its surgical treatment. Although benign multicystic mesothelioma is a rare pathologic entity, it is important that sonologists include it in the differential diagnosis of diseases that manifest with ascites. Furthermore, all surgeons should be aware of the macroscopic and laparoscopic appearance of the lesion, and its generally benign course.