There are three main cellular subtypes of mesothelioma. Epithelial mesothelioma makes up the majority of cases, followed by biphasic, and sarcomatoid is the least common. Biphasic tumors are made up of a mixture of sarcomatoid and epithelioid cells. Sarcomatoid types make up only about 15 percent of all cases of mesothelioma and even rarer is a subtype of sarcomatoid cells called desmoplastic mesothelioma.
Desmoplasia refers to the growth of connective and fibrous tissue, but it is not always malignant or associated with malignant cancer. This fact means that malignant mesothelioma of this subtype is often misdiagnosed as something benign. Diagnosis is important for desmoplastic mesothelioma, as is quick treatment; like all sarcomatoid mesotheliomas, this subtype is aggressive and spreads quickly.
The term desmoplasia refers to any type of growth of fibrous connective tissue. It is typically a reactive growth in that it begins in response to something else, like a tumor or scar tissue from injuries or surgeries. Although the fibrosis is not always malignant, it does usually invade surrounding healthy tissue, which can be a problem. When mesothelioma is of the desmoplastic cell subtype, this invasion of the fibrosis is often what leads to a diagnosis.
Characteristics of Desmoplastic Mesothelioma
Desmoplastic mesothelioma is rare, accounting for just about five percent of cases of this type of asbestos-related cancer. Because it is rare, information about it is limited. One study investigated several cases, though, and found that about 88 percent of people diagnosed with desmoplastic mesothelioma had already experienced metastases. The cancer had spread to distant parts of the body. This is typical of all types of sarcomatoid mesothelioma, which are generally more aggressive than epithelial cancers.
The appearance of the tumor under the microscope included dense bundles of collagen fibers, a type of connective tissue. Even when this collagen had a spindled order, the arrangement was typically irregular, a characteristic that can be useful in diagnoses. Seventy-five percent of cases showed collagen death, which appeared on the cellular level as bland and without inflammation.
Apart from the histological characteristics, desmoplastic mesothelioma causes similar symptoms to other types. Most cases are pleural, which causes shortness of breath, coughing, and chest pain. Some cases have been found to be peritoneal mesothelioma, which causes abdominal swelling, pain, and indigestion. Very rarely, this subtype has been seen in pericardial mesothelioma.
Generally, diagnosis of any type of mesothelioma begins with a physical examination followed by imaging tests like X-rays and CT scans. If these show any signs of unusual tissue growth, a biopsy is likely done next. This involves removing a small amount of fluid or tissue from the tumor or area that is suspected to be cancerous. A pathologist examines the sample at the cellular level to try to determine what type of cancer it is, and if mesothelioma, what subtype.
Diagnosing the desmoplastic type of mesothelioma can be tricky. The tissue involved looks bland and closely resembles benign fibrous tissue. For this reason malignant desmoplastic mesothelioma may be misdiagnosed as pleural fibrosis. Some of the diagnostic criteria used to confirm desmoplastic mesothelioma include that more than half of the tumor is dense fibrous tissue, that there are features of sarcomatoid cancer, that there is collagen tissue death, and that the tumor has invaded surrounding tissue.
One study investigated over 300 cases of sarcomatoid mesothelioma and found that using immunohistochemistry to make diagnoses is particularly useful. It has been used to distinguish between different subtypes of sarcomatoid mesothelioma, including desmoplastic mesotheliomas. This diagnostic technique uses tissue samples from a biopsy and antibodies. These are proteins of the immune system that normally detect pathogens, but they can also be used to detect the proteins called antigens that are specific to different types of cancer cells.
As with any type of mesothelioma, the treatment for desmoplastic mesothelioma varies depending on the stage of the cancer, the individual’s age and health, and other factors. The three most common types of treatment are chemotherapy, radiation therapy, and surgery. Surgery is less commonly used with this type of mesothelioma because it is often not indicated for cancers that have already metastasized. Most cases of desmoplastic mesothelioma are diagnosed when the cancer is already in a late, metastatic stage.
Chemotherapy can be used to shrink the tumors, as can radiation. Radiation is more targeted to specific tumors and causes fewer side effects. Chemotherapy is systemic, meaning it is administered to the entire body and attacks all cells that grow and divide rapidly. This makes it more effective than other treatments, but it also causes a lot of unpleasant side effects.
For most people being treated for desmoplastic mesothelioma, the purpose is palliative. The treatments may extend the patient’s life, but mostly are used to reduce symptoms. By shrinking the tumors, the patient may be able to breathe easier and will likely experience less pain. Because this type of cancer typically causes fluid to build up between tissue layers, draining that fluid is also helpful in reducing pain and increasing comfort for patients.
The prognosis for desmoplastic mesothelioma is not usually very positive. Because mesothelioma generally, and this subtype in particular, is hard to diagnose, most people don’t find out they have it until the cancer is in the later stages. At this point it is virtually impossible to cure, and the life expectancy is not very long. The duration of survival for desmoplastic mesothelioma, according to one study, is between five and seven months after diagnosis. At this point treatments can be used for palliative care.
If you have any symptoms that could indicate any type of mesothelioma, getting a diagnosis as soon as possible is crucial. Mesothelioma is rare, but if you know you have spent time around asbestos, you may have developed this type of cancer. Regardless of the cellular subtype, mesothelioma is difficult to treat and has poor survival rates. Getting checked out and eliminating mesothelioma or getting a diagnosis for it is the best thing you can do for your future and your loved ones.
Page edited by Dave Foster
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