Cystic mesothelioma is a very rare form of this type of cancer. It is also called multicystic mesothelioma of the peritoneum or multicystic peritoneal mesothelioma because it is a cancer that begins in the peritoneum in the abdominal cavity. Research on this type of mesothelioma is limited because there have been so few cases reported.
The tumors that grow in this type of mesothelioma have a distinctive cell type and grow with multiple cysts in them. They are most often benign and surgical removal is often enough to cure the condition. In some cases, however, this kind of cancer can turn malignant. It becomes aggressive and spreads quickly, making it difficult to treat.
Incidence of Cystic Mesothelioma
The incidence of multicystic peritoneal mesothelioma is very low. Only about 150 diagnoses have been made and reported in the medical literature. What is known from these few case studies is that it most often occurs in women during their child-bearing years. In most cases the tumor originated in the pelvic region of the peritoneum. In some cases it began in the peritoneum near the bladder, uterus, or rectum, or in the omentum, a layer of fat that covers the abdominal cavity. In the few men with this condition the tumor most often originates 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 people to study 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 the development of the tumor. Irritation from a surgery or from endometriosis—a condition characterized by growth of uterine tissue outside of the uterus—that occurs chronically over time may be another possible cause of cystic mesothelioma.
The most common symptoms of this type of cancer, which appear most often in the few cases, are abdominal pain and a mass that can be felt in the abdomen. These are the symptoms that led most women with the condition to see a doctor for a diagnosis. Additionally, there may be other symptoms: absence of menstruation, painful sexual intercourse, difficult or painful urination, and weight loss.
Cell Type Characteristics
The tumors of multicystic peritoneal mesothelioma are fairly distinct from those of other mesotheliomas. They include cells that are mostly epithelial, but there may also be sarcomatoid cells in the tumor. The most characteristic aspect of these tumors is the presence of multiple cysts within it. These are usually fluid-filled and can become as large as 20 centimeters in diameter.
Because the tumor is so distinct from other mesothelioma tumors, diagnosing this cystic type of cancer is usually straightforward. When a patient has abdominal symptoms and a physical exam reveals a palpable mass, the next step is usually to use a CT scan, ultrasound, or MRI to image the abdominal cavity. This can show the mass in greater detail.
A biopsy can then be performed to withdraw fluid and cells from the tumor to be investigated by a pathologist. As compared to a malignant mesothelioma tumor, a benign multicystic tumor will have many fluid-filled cysts instead of being made up of multiple smaller tumors, called nodules. Immunohistochemical staining can even more accurately identify the cells of a benign tumor by specifically targeting them with antibodies.
Malignant Cystic Mesothelioma
Multicystic peritoneal mesothelioma is overwhelmingly benign. In the few known cases it is almost always benign and curable. However, rarely this type of cancer may become unexpectedly malignant and aggressive. In one case study, a 36-year-old woman was diagnosed with benign cystic peritoneal mesothelioma and underwent six separate surgeries to reduce the mass of the large tumor. As her doctors tracked the progression of the tumor and the treatments, they discovered that it had transformed into malignant cancer and had invaded other tissues including the lymph nodes.
When cystic mesothelioma is benign, and remains benign, it is highly treatable and has very high survival rates. The treatment is surgery to remove the mass or to reduce its size and drain fluids from the cysts if it is not possible to remove the entire tumor. Surgical removal of the tumor can be curative, but some patients have a recurrence several years later. Even with a recurrence, most patients simply need to have surgery again to remove the new tumor and cysts.
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