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Cystic mesothelioma is a very rare form of mesothelioma. Also called multicystic mesothelioma of the peritoneum or multicystic peritoneal mesothelioma, this cancer originates in the peritoneum of the abdominal cavity. Because there are so few reported cases, there has been scant research on cystic mesothelioma.
Tumors that form with this type of mesothelioma have a distinctive cell type and grow with multiple cysts. These tumors are most often benign and surgical removal is enough to cure the condition. In some cases, however, this cancer becomes malignant. Once malignant, the cancer becomes aggressive and spreads quickly, making it difficult to treat. Untill now, there has been only a couple of cases where benign cystic mesothelioma became malignant. These cases include a 6-months old baby and 36years of female.
Incidence of Cystic Mesothelioma
Incidence of multicystic peritoneal mesothelioma is low. Approximately 150 diagnoses have been reported in the medical literature. From these case studies, experts have found cystic mesothelioma most often occurs in women of child-bearing age. In most cases, the tumor originated in the pelvic region of the peritoneum. However, in some cases, it originated in the peritoneum near the bladder, uterus, rectum, or in the omentum, a layer of fat that covers the abdominal cavity. In the few men diagnosed, the tumor most often originated in the peritoneum around the rectum and bladder.
Unlike other types of mesothelioma, there is no link between cystic mesothelioma and asbestos exposure. With so few cases, it is hard to determine what does cause this type of cancer. Because it occurs mostly in women, it may be related to hormones, which could trigger tumor development. Irritation from surgery or from endometriosis, a condition characterized by growth of uterine tissue outside of the uterus, occurring chronically is another possible cause.
The most common symptoms of cystic mesothelioma, are abdominal pain and a mass in the abdomen. There may be other symptoms, including absence of menstruation, painful sexual intercourse, difficult or painful urination, and weight loss.
Cell Type Characteristics
Tumors of multicystic peritoneal mesothelioma are distinct from other mesotheliomas. These tumors include cells that are mostly epithelial. However, there may also be sarcomatoid cells present. The most characteristic aspect of these tumors is the presence of multiple cysts. These cysts are usually filled with fluid and can become as large as 20 centimeters in diameter.
Because the tumor is so distinct from other mesothelioma tumors, diagnosing this cancer is usually straightforward. When a patient has abdominal symptoms and physical exam reveals a palpable mass, the next step is a CT scan, ultrasound, or MRI to image the abdominal cavity. These images show the mass in greater detail.
A biopsy is then performed to withdraw fluid and cells from the tumor. A pathologist then examines the sample. As compared to a malignant mesothelioma tumor, a benign multicystic tumor will have many fluid-filled cysts instead of multiple smaller tumors, called nodules. Immunohistochemical staining can more accurately identify cells of a benign tumor by specifically targeting them with antibodies.
Malignant Cystic Mesothelioma
Multicystic peritoneal mesothelioma is overwhelmingly benign. However, these tumors may become unexpectedly malignant and aggressive. In one case study, a 36-year-old woman was diagnosed with benign cystic peritoneal mesothelioma. She underwent six separate surgeries to reduce the mass of the large tumor. As her doctors tracked progression of the tumor, they discovered it had transformed into malignant cancer, invading tissue including the lymph nodes.
When cystic mesothelioma is benign, it is treatable and has a high survival rate. Treatment is surgery to remove the mass. If removal is not possible, surgery may aim to reduce size and drain fluids from the cysts. Surgical removal can be curative. However, some patients have a recurrence several years later. However, even with recurrence, most patients simply have another surgery to remove the tumor or cysts.
Page Medically Reviewed and Edited by Pinar Kanlikilicer, PhD
Dr. Pinar Kanlikilicer has a PhD in Biomedical Engineering. She completed her 5-years of postdoctoral training in the Department of Experimental Therapeutics at MD Anderson Cancer Center. She is currently working in the field of cancer as a research scientist.