Deciduoid Mesothelioma
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Mesothelioma may be rare, but it comes in many different forms, each characterized by cell type. Pathologists use tissue biopsy samples to determine cell type. Cell type is an important distinguishing factor in mesothelioma. It helps medical professionals determine the best course of treatment. One form is deciduoid, a cell type that is very rare in mesothelioma.
Deciduoid cells are subtypes of epithelioid cells, the most common cell type in mesothelioma. Deciduoid mesothelioma is so rare it has only been documented in a handful of cases. Most cases have been young women with peritoneal mesothelioma. This type of mesothelioma attacks the lining of the abdominal organs. As with most types of mesothelioma, treatment is rarely curative and the prognosis is not positive.
Epithelioid Mesothelioma
Epithelioid mesothelioma is one main classification of this cancer by cell type. Epithelial cells are most commonly seen in mesothelioma, accounting for about 70 percent of diagnosed cases. Epithelial cancer is easier to treat than sarcomatoid, the next most common type. Because epithelial cells adhere together strongly, they are less likely to spread to other parts of the body. These cells will eventually metastasize (spread to other parts of the body) but do so more slowly than sarcomatoid mesothelioma.
Deciduoid Cells
These cells are called deciduoid because they look similar to cells seen in early pregnancy. In the early stages of pregnancy, hormone shifts trigger cellular changes in the uterus. The cells lining the organ change shape and purpose. This change helps the placenta develop and pregnancy to progress normally. After this shift occurs, the cells and lining of the uterus are called decidua. However, deciduoid mesothelioma cells are not the same. Instead, they simply resemble the uterine cells. Histologically, patients with deciduoid mesothelioma has large, polygonal or ovoid cells with well-defined cell borders, and single or multiple nuclei.
Facts about Deciduoid Mesothelioma
Deciduoid cells are a sub-type of epithelial cells. Mesothelioma comprised of deciduoid cells are extremely rare. Mesothelioma is overwhelmingly more common in older men. However, deciduoid mesothelioma most often strikes young women. It is possible to see deciduoid mesothelioma in older men and women. However, this is rare.
Another unusual characteristic of deciduoid mesothelioma is the half-and-half distribution between pleural and peritoneal deciduoid mesothelioma. With other cell types, about 75 percent of cases are pleural. Because of the way it forms, as well as because it so often afflicts young women, many experts believe this mesothelioma is not related to asbestos exposure. Asbestos exposure causes the vast majority of mesothelioma cases. If this is correct, deciduoid mesothelioma is quite unusual.
Causes of Deciduoid Mesothelioma
This type of mesothelioma is so rare that it is difficult to determine what causes it. Many experts believe this type is not completely related to asbestos exposure. For most other types of mesothelioma, asbestos is the predominant risk factor. However, that does not seem to be the case with deciduoid mesothelioma. Only about one third of people diagnosed were ever exposed to asbestos.
One hypothesis on the cause of this mesothelioma is that hormones are related to deciduoid mesothelioma. More than half of reported cases were in women. In two of those cases, the women were pregnant. It may be hormonal imbalances trigger the cancer development. However, few tests support this hypothesis.
Diagnosis
Deciduoid mesothelioma diagnosis is problematic because it is so rare. It also closely resembles other illnesses, including more common types of peritoneal mesothelioma, a cancer which is also rare. Many symptoms of peritoneal mesothelioma are similar to more common conditions like irritable bowel syndrome, including bloating, indigestion, and abdominal pain.
Even when mesothelioma is diagnosed, it can be hard to determine that someone has deciduoid mesothelioma specifically. The amount of the tumor that resembles the decidua varies by patient, making diagnosis even more difficult. Another complication is the tumor often resembles pseudotumoral deciduosis, another type of mesothelioma. Also, this type of tumor often occurs in pregnant women when they are pregnant. However, these tumors are not cancerous, though misdiagnosing mesothelioma as pseudotumoral deciduosis can be serious. A mistaken diagnosis can delay life-saving treatment required for mesothelioma.
Treatment and Prognosis
As with all types of mesothelioma, treating deciduoid tumors is difficult and almost never curative. It is often diagnosed in later stages when it is well-developed and spread. Surgery may be an initial treatment choice for tumor removal, but, if the cancer has spread to other parts of the body, surgery may not be a viable option.
Multi-modal treatment is the most common choice. This treatment approach uses several strategies to try to reduce the size and number of tumors. Multi-modal treatments generally use surgery, chemotherapy, and radiation in some combination. A surgeon can remove the bulk of a tumor, while radiation and chemotherapy shrink tumors or eliminate remaining cancer cells after surgery.
Unfortunately, the prognosis for deciduoid mesothelioma typically not positive. Survival rates are low, with a shortened life expectancy for most patients. With so few cases available to study, it is difficult to estimate life expectancy. However, only about one third of deciduoid mesothelioma patients survived a year after a diagnosis. According to a meta analysis study, while patients with tumors that present highly aggressive clinical behavior have a mean survival rate of 7 months, patients with tumors that exhibit less aggressive clinical features have a mean survival rate of 23 months.
Treatments can extend life for some. For others, treatment simply reduces pain and increases mobility, generally improving the remaining quality of life.
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.
