Sarcomatoid Mesothelioma


Sarcomatoid Mesothelioma cells are the least common of the mesothelioma cell types and are the most resistant to cancer therapies. Diagnosis is challenging because the cells can resemble other cancers. Treatment will depend on cancer's stage and your overall health. Sarcomatoid mesothelioma is characterized by spindle-shaped cells that produce very aggressive and difficult to treat tumors. As the rarest form of mesothelioma, only 10 per cent of all cases are strictly sarcomatoid, though sarcomatoid cells are also found in biphasic mesothelioma. Sarcomatoid pleural mesothelioma is the most aggressive type of mesothelioma. This type of mesothelioma is formed by sarcomatoid cells and is located in the pleura or the lining of the lungs. Sarcomatoid is the least common cell type of mesothelioma and can affect treatment and prognosis.

What is Sarcomatoid Mesothelioma?

Sarcomatoid cells metastasize faster than other mesothelioma cell types, causing the formation of cancerous tumors in other areas of the body. This makes sarcomatoid the most dangerous cell type, though new treatments are leading to longer life expectancies. Sarcomatoid mesothelioma only accounts for about 10-15 per cent of all mesothelioma diagnoses. Sarcomatoid mesothelioma is very hard to diagnose, and many patients are misdiagnosed at first.

In addition to being very rare, sarcomatoid mesothelioma cells can look like healthy tissue, making it even harder to determine whether they are malignant. The only way to tell for sure is to take a tissue sample by biopsy and send for laboratory analysis. These cells appear elongated, spindle-shaped and often form a fibrous pattern that resembles a tumor called histiocytoma. Some epithelioid cells may be present within sarcomatoid tumors, but by definition, they must make up less than 10 per cent of the tumor’s mass.
Variants of this form of cancer include transitional, lymphohistiocytoid and desmoplastic mesothelioma. Like most other types of the disease, the sarcomatoid cell type is linked to asbestos exposure.

Characteristics of Sarcomatoid Cells

Cell Description

The cells are spindle-shaped and have an enlarged, elongated nucleus. These cells sometimes have multiple nuclei and are harder to distinguish from healthy tissue.

Cell Behavior

Sarcomatoid cells do not bundle themselves in a uniform way like epithelioid cells. This contributes to the cells’ ability to spread faster than other cell types.

Where it occurs

Sarcomatoid mesothelioma is most frequently found in the pleural cavity. The lungs are lined with two mesothelial layers that allow the lungs to expand and contract within the chest. Gradually, asbestos particles trapped in the lining can cause cancer cells to grow, eventually restricting the lungs from moving freely.

Sarcomatoid cells are found with epithelioid cells in approximately 30 – 40 per cent of all mesothelioma cases, a situation is known as biphasic mesothelioma. This form of mesothelioma most frequently occurs in the lining around the abdomen (peritoneal mesothelioma) and in the lining around the heart (pericardial mesothelioma).

How it develops

Asbestos exposure is connected to most cases of sarcomatoid mesothelioma. The asbestos type most closely connected to mesothelioma has small, needle-like fibers that, once inhaled, puncture the lungs and slowly work their way through the tissue until they are lodged in the lining of the lung.
Once asbestos is lodged in the mesothelium, they can create inflammation and cause the cells to mutate, thus forming cancer.

Sarcomatoid Mesothelioma

Sarcomatoid Is the Most Aggressive Cell Type

About 10 to 20 percent of pleural mesotheliomas and fewer than 4 percent of peritoneal mesotheliomas are made up of this cell type.
  • Linked to asbestos exposure.
  • Tumors appear as nodules or lesions, with or without effusion, and rarely as a localized mass.
  • More resistant to treatment than other cell types.
  • Tumors are composed of giant, spindle-shaped cells in fibrous bundles.

Sarcomatoid Mesothelioma Subtypes

There are several subtypes of sarcomatoid mesothelioma.


This biphasic (but prominently sarcomatoid) form of mesothelioma consists primarily of a bundle of immune cells.


This essentially sarcomatoid cell-type is described as “bland.” It is frequently misdiagnosed as a benign fibroid.


The rarest of the rare, these cell-types are different than the tissues in which the cancer is formed, for instance, bone cells may be found in tumors not attached to the bone.


Exceedingly rare, this mesothelioma cell-type is made of bone cells.


These spindle cells are from cartilage.

Survival and Staging

Sarcomatoid mesothelioma makes up only 5 – 10 percent of all mesothelioma cases, and fewer studies have looked at sarcomatoid types than epithelioid or biphasic types. As a result, there are no large studies that can accurately show survival rates by stage.
Cancer staging relies on measuring the tumor size, the spread to the lymph nodes, and the presence of metastasis. For all types of mesothelioma, the survival rates range from stage 1 at 21 months to stage 4 at 12 months. As already mentioned, it’s considerably less for those diagnosed with sarcomatoid tumors.

Sarcomatoid Mesothelioma Symptoms and Diagnosis

Sarcomatoid cell types are found in 10-20 percent of pleural mesothelioma and in 4 percent of peritoneal mesothelioma diagnoses. They are also found in bladder, kidney, lung, and liver cancers.
The diagnosis of sarcomatoid mesothelioma is difficult because of the similarity to benign tissue cells. Sarcomatoid mesothelioma is commonly misdiagnosed as fibrous pleurisy, fibrosarcoma, and metastasized renal cell carcinoma.

Knowing the symptoms of the disease can prepare patients for what to expect. Symptoms get more intense as tumors begin to spread. Below are some general symptoms of sarcomatoid mesothelioma. Most sarcomatoid mesothelioma develops in the pleura (lining of the lungs); however, other symptoms may appear if it develops in the abdominal lining (peritoneum). In general, the symptoms experienced will depend more on the location of the tumor than the mesothelioma cell type. Diagnosing sarcomatoid pleural mesothelioma is difficult because sarcomatoid tumors often resemble benign and other malignant conditions, and an initial misdiagnosis is possible. Under a microscope, sarcomatoid tissue samples can appear similar to sarcoma tumors and localized tumors of the pleura.

Symptoms of sarcomatoid mesothelioma of the pleura include:

  • Weight loss
  • Fatigue
  • Shortness of breath
  • Difficulty breathing

Symptoms of sarcomatoid mesothelioma of the peritoneum include:

  • Loss of appetite
  • Nausea
  • Pain of the abdomen
  • Swelling
Since sarcomatoid cells are so hard to differentiate from other cell types, doctors use a process called immunohistochemistry. This process is a tissue staining technique that makes proteins in the cell samples more visible under a microscope. Diagnosing this type of pleural mesothelioma may also be difficult because symptoms of pleural mesothelioma can mimic symptoms of other, less serious respiratory illnesses, including pneumonia or asthma.


Individuals who begin to experience mesothelioma symptoms should seek medical attention right away. The sooner doctors can begin their diagnostic tests, the better chance of survival. This is especially true for anyone who has a history of asbestos exposure.

Because sarcomatoid cells look similar to healthy tissue, this type of mesothelioma is very difficult to diagnose correctly. It can easily be confused for different sarcomas or other forms of lung cancer. Diagnosing this cell type is difficult because these tumors tend to mimic other benign and malignant conditions in appearance. When pathologists examine these tissue samples under a microscope, the cells resemble those of sarcoma tumors and localized fibrous tumors of the pleura. Because of the aggressive nature of this tumor type, the prognosis is not as favourable as other cell types, and treatment options are not as plentiful. The poor survival rates associated with this cell type make accurate diagnosis even more imperative.

After taking the patient’s medical history, the doctor will usually order imaging tests, such as an X-ray, CT scan, or MRI. The radiologist will review the images for tumor tissue or any other abnormalities that could explain the symptoms. If warranted, additional tests will be conducted.


Mesothelioma frequently causes fluid to build up around the lungs. This fluid can be extracted using various methods and then tested for various biomarkers – components that point to a particular type of disease.

Physicians biopsy the tumor by making a small incision near the tumor. Until now, the tests have been checking to see if there is a problem. Once they have biopsy material, they can finally discover what type of disease the patient has.


The biopsied tissue will provide a pathologist with enough information to diagnose the disease. For instance, the surest way to distinguish sarcomatoid mesothelioma from various sarcomas is to test the tissue for a substance called cytokeratin. Sarcomatoid mesothelioma tumors express this protein, while the similar looking sarcomas do not.

They will also perform a test called nuclear grading. This examines the nucleus of the cells and compares them to samples of known diseases.

Treatment for Sarcomatoid Mesothelioma

Given the aggressiveness of sarcomatoid tumors, the prognosis for this cell type is not as favourable as other cell types, and there are not as many treatment options available.
Like other cell types, treatment is dependent on the stage of cancer and the location of the tumor. This means that conventional treatment such as surgery, chemotherapy and radiation therapy may be options for those diagnosed with this cell type. Unfortunately, sarcomatoid cells are more resistant to treatment, especially if diagnosed in its later stages.

In particular, sarcomatoid pleural mesothelioma is difficult to treat with surgery, because these tumors typically penetrate the chest wall and can become difficult and more complicated to remove. Unfortunately, chemotherapy also has had limited success in treating sarcomatoid pleural mesothelioma. Treatment for sarcomatoid cell types is difficult because it is the most aggressive cell type of mesothelioma. Although surgery, chemotherapy, and radiation are the treatment options most used with sarcomatoid mesothelioma, surgery can be difficult.
Sarcomatoid mesothelioma is very rigid when it attaches to the chest wall and it is difficult to remove. In peritoneal mesothelioma instances, the tumor cases around the intestines which also makes it harder to remove.

Although chemotherapy does not show as much success in shrinking tumors, there have been new discoveries made. Researchers have discovered that a drug called doxorubicin works effectively on its own and when combined with other chemotherapy drugs.
Surgery is difficult because sarcomatoid tumors are more difficult to remove than tumors made of other cell types, and they metastasize quickly. Chemotherapy has proven to be nearly ineffective, as the sarcomatoid cells are resistant. Radiation therapy relies on the ability to isolate the cancer-affected area from healthy tissue, something that mesothelioma rarely provides.

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This said, if a patient is diagnosed with sarcomatoid mesothelioma, supportive and palliative care is still available in most cases.

Researchers are working on new and experimental treatments which may prove to be more effective in the future. Immunotherapy removes some immune cells from the patient and modifies them to attack the mesothelioma. Similarly, viruses are modified to attack the mesothelioma which changes the tumor genes, causing the mesothelioma to die with gene therapy. These new therapies are still in the research phase.

There may be hope in a newer drug called sodium selenite, which has so far proven to be a more potent chemotherapy drug for all mesothelioma cell types, including sarcomatoid. Research has shown that sodium selenite combined with doxorubicin, an anthracycline antibiotic, has caused apoptosis, or cell death. But no human studies have been conducted yet. Another chemotherapy drug combination that has produced favourable results in some cases is known as CYVADIC chemotherapy, which incorporates several medications, including cyclophosphamide, vincristine, doxorubicin, also called adriamycin, and dacarbazine, also called DTIC. However, the response rate is usually low, which is why this therapy isn’t commonly used to treat pleural mesothelioma.


Sarcomatoid cells have proven to be more resistant to treatment than other types of mesothelioma. Surgery, in particular, can be difficult because these tumors are very rigid and often grow into the chest wall, making them especially difficult to remove. In cases of peritoneal tumors, the cancer usually encases the soft internal organs of the abdomen, which can make the identification and removal of the primary tumor challenging.


Chemotherapy has also displayed limited success rates for this cell type. One case report described an encouraging result using a chemotherapy regimen used to treat sarcomas, CYVADIC, which incorporates cyclophosphamide, vincristine, doxorubicin and dacarbazine.

Features and Diagnostic Techniques

Pathological examination reveals these tumors form nodules that invade surrounding tissues, including the fat found in the parietal pleura. When viewed under a microscope, the tissue contains spindle-shaped cells arranged in a haphazard pattern with plump, elongated nuclei. The same pattern is often seen in fibrosarcoma tumors and thus contributes to misdiagnosis. Sometimes sarcomatoid mesothelioma cells can have more than one nucleus, which makes the tumor easily confusable with fibrous histiocytoma.

To better differentiate mesothelioma from other cancers, pathologists use a tissue staining technique called immunohistochemistry. This technique enhances cell samples with diagnostic markers that react to specific proteins in the tumor tissue. Pathologists can look for these reactions under a microscope to make a diagnosis and determine the cancer’s cell type.

A 2015 study explains the most useful markers for diagnosing mesothelioma include cytokeratin 5/6, podoplanin, WT1 and calretinin. The authors of the study add that sarcomatoid tumors may not react to most markers in a majority of cells, however, which makes an accurate diagnosis difficult. They conclude that calretinin and podoplanin are more likely to be effective in diagnosing sarcomatoid mesothelioma, but note a wide variation among laboratories in diagnostic marker choices.


The median survival for patients with sarcomatoid tumors is typically less than six months, but some patients live longer, depending on factors like age and overall health. Patients with the lymphohistiocytoid variant of this cell type have survived for as long as six years, and there are reports of spontaneous tumor remission.

Finding clinical trials designed for sarcomatoid patients may be difficult. Certain speciality cancer centres, like the UCLA Jonsson Comprehensive Cancer Center in Los Angeles, offer programs dedicated to providing more treatment options and expertise than standard cancer care facilities. 
The prognosis for sarcomatoid cell mesothelioma is not as positive as other cell types. The median survival rate for patients is around six months. However, there have been patients that have survived up to six years past their initial diagnosis date. Patients with lymphohistiocytic mesothelioma have the best prognosis.

A patient’s prognosis is largely dependent upon available treatment options and the cancer’s stage at the discovery. Every prognosis, no matter how dire, has had cases of survival. There have been survivors living with mesothelioma for 5+ years after a sarcomatoid mesothelioma diagnosis.



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Mesothelioma Master: Sarcomatoid Mesothelioma
Sarcomatoid Mesothelioma
Sarcomatoid mesothelioma is very hard to diagnose, and many patients are misdiagnosed at first.This makes sarcomatoid the most dangerous cell type.
Mesothelioma Master
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