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Deciduoid Mesothelioma

Mesothelioma may be a rare type of cancer, but it comes in a lot of different forms and variations and cell types. One of these is deciduoid, a cell type that is very rare in mesothelioma. Cell type is an important distinguishing factor in mesothelioma because it helps doctors and specialists determine the best course of treatment. Pathologists use biopsy samples of tissue from patients to try to diagnose the cell type once cancer has been diagnosed.

Deciduoid cells are subtypes of epithelioid cells, the most common cell type in mesothelioma. Deciduoid mesothelioma is so rare that it has only been documented in a handful of cases, first described in 1985. Most cases have been seen in young women with peritoneal mesothelioma, the type of this cancer that 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 of the main classifications of this type of cancer by cell type. Epithelioid or 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. These cells are less likely to spread because they adhere strongly to each other. They will eventually metastasize, or spread to other tissues and parts of the body, but do so more slowly than in sarcomatoid mesothelioma.

Deciduoid Cells

The term deciduoid was given to the cells seen in this rare type of mesothelioma because they look similar to cells that are 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 and help the placenta to develop. The cells and the lining of the uterus after this shift occurs are called decidua. The deciduoid cells of this rare type of mesothelioma are not the same; they simply resemble the uterine cells.

Facts about Deciduoid Mesothelioma

Deciduoid cell types are epithelial cells, but a subtype. Cases of mesothelioma that can be classified as being made up of deciduoid cells are extremely rare. One of the most unusual characteristics of this type of mesothelioma is that it most often strikes young women. Overall, mesothelioma is overwhelmingly more common in older men. It is possible to see deciduoid mesothelioma in older men and women, but it is very rare.

Another unusual characteristic is that the distribution between pleural and peritoneal deciduoid mesothelioma is just about half and half. With other cell types, about 75 percent of cases are pleural. Because of how it forms and the demographic, many experts that have looked into this rare kind of mesothelioma believe that it is not related to asbestos exposure. The vast majority of cases of mesothelioma are caused by asbestos so this is one more characteristic that makes deciduoid mesothelioma so unusual.

Causes of Deciduoid Mesothelioma

This type of mesothelioma is so rare, and the number of case studies so limited, that it is difficult to say what causes it. Many experts believe that, unlike most cases of mesothelioma, this type is not always or completely related to asbestos exposure. For most other types of mesothelioma, asbestos is the overwhelmingly predominant risk factor, but that doesn’t seem to be the case for deciduoid mesothelioma. Only about one third of people diagnosed with it were ever exposed to asbestos.

One hypothesis about what causes deciduoid mesothelioma concerns hormones. More than half of all the reported cases were in women; in two cases the women were pregnant. It may be that hormonal imbalances trigger the development of the cancer. Not many tests have been able to support this hypothesis, however.


The diagnosis of deciduoid mesothelioma is tricky because it is so rare and because it so closely resembles other illnesses, including more common types of peritoneal mesothelioma, a cancer which itself is rare. Many of the symptoms of any type of peritoneal mesothelioma are similar to more common conditions like irritable bowel syndrome: bloating, indigestion, and abdominal pain.

Even when cancer and mesothelioma are diagnosed it can be hard to determine that someone has deciduoid mesothelioma. How much of the tumor resembles the decidua varies by patient and this can make it difficult to diagnose. Another complication is that the tumor resembles that of another type called pseudotumoral deciduosis. This type of tumor is often found in women when they are pregnant, further complicating the diagnosis. This tumor is not cancerous, though, so misdiagnosing mesothelioma as pseudotumoral deciduosis can be very serious. It can delay the life-saving treatment required for mesothelioma.

Treatment and Prognosis

As with all types of mesothelioma, treating deciduoid tumors is not easy and almost never curative. It is often diagnosed in the later stages of the cancer when it is already developed and possibly spread. All types of mesothelioma are aggressive and spread quickly, making treatment challenging. Surgery may be an initial treatment choice to remove the tumor, but if the cancer has spread to other parts of the body, it may not be possible.

Multimodal treatment is the most common choice, which means using several strategies to try to reduce the size and number of tumors in the body. This may involve using surgery, chemotherapy, and radiation in some combination. Surgery can be used to remove the bulk of a tumor, while radiation and chemotherapy are used to shrink tumors or eliminate any remaining cancer cells after surgery.

Unfortunately the prognosis is generally not good for deciduoid mesothelioma. Survival rates are low and most patients will have a shortened life expectancy. With just a few dozen cases available to study, it is hard to give a good estimate for life expectancy, but only about one third of people with deciduoid mesothelioma survived a year after a diagnosis. Treatments can extend life for some patients, but for others may be used to reduce pain and increase mobility and to generally improve the remaining quality of life.

Page edited by Dave Foster

Dave has been a mesothelioma Patient Advocate for over 10 years. He consistently attends all major national and international mesothelioma meetings. In doing so, he is able to stay on top of the latest treatments, clinical trials, and research results. He also personally meets with mesothelioma patients and their families and connects them with the best medical specialists and legal representatives available.

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