Sarcomatoid Mesothelioma

What Is Sarcomatoid Mesothelioma?

Sarcomatoid mesothelioma is a rare variant of asbestos cancer made up of sarcomatoid cancer cells. This mesothelioma type is also more aggressive and resistant to treatment than the epithelial or biphasic cell types because the tumor cells quickly spread, or metastasize, to new areas.

Tumors with this cell type appear fibrous and diffuse throughout the pleura, the term for the pleural membrane surrounding the lungs and lining the chest cavity. There are fewer than 30 documented cases of sarcomatoid peritoneal mesothelioma.

The fibrous nature and rapid growth of sarcomatoid cells make this type of mesothelioma especially difficult to treat. Pathologists specializing in mesothelioma can identify some of these rare cellular features when viewing tissue samples under a microscope.

“If you’ve been diagnosed with mesothelioma, I would encourage you to not look at those statistics and life expectancies and think that is your future. Everyone is different with this diagnosis. It’s really important to speak to those specialists who deal with this disease to determine what your future is going to be.”

Karen Selby

Registered nurse and Patient Advocate at The Mesothelioma Center at Asbestos.com

Rare Sarcomatoid Mesothelioma Cell Subtypes

Epithelial, biphasic and sarcomatoid are the three primary cell types of mesothelioma tumors. However, pathologists further distinguish primary cell types into subtypes judged by distinctive characteristics within each variant.

There are three rare sarcomatoid mesothelioma cell subtypes.

Transitional Mesothelioma: This variant tends to grow and spread in ways similar to other sarcomatoid mesotheliomas. It has fat, spindle-shaped cells, which helps pathologists differentiate it from other cells.

Lymphohistiocytoid Mesothelioma: These tumors contain inflammatory and immune cells. The lymphohistiocytoid variant makes up less than 1% of all mesotheliomas. Some patients with this cancer have a better-than-average life expectancy.

Desmoplastic Mesothelioma: This sarcomatoid subtype is one of the most difficult to diagnose. Half or more of the tumor shows no discernible pattern of growth. Desmoplastic type accounts for approximately 5% of all mesotheliomas.

While these sarcomatoid mesothelioma subtypes are exceedingly rare, they tend to have a higher tendency to metastasize and are correlated with a poor prognosis.

The pleura is the most likely location for rare sarcomatoid cell types to develop, but the desmoplastic variant has occurred in some cases of peritoneal and testicular mesothelioma.

“Sarcomatoid cell types – these are slightly more aggressive tumors.”

Dr. Jacques Fontaine

What Causes Sarcomatoid Mesothelioma?

Sarcomatoid mesothelioma causes are primarily from asbestos sources. After breathing in or swallowing asbestos fibers, tiny fragments of the toxic mineral can become trapped in the body. Over decades, irritation and inflammation cause mutations that lead to mesothelioma cancer.

Mesothelioma symptoms often take 20 to 60 years to appear after asbestos exposure and can mimic other, more common illnesses. People with a history of asbestos exposure should speak with their doctor about early screening for sarcomatoid mesothelioma and other asbestos-related diseases.

Symptoms of Sarcomatoid Mesothelioma

Because sarcomatoid mesothelioma is almost exclusively found in the pleural membrane, most patients experience nonspecific respiratory symptoms such as cough and shortness of breath.

Patients also commonly experience chest pain. As the disease progresses, symptoms become more serious. It’s essential to speak with a specialist about any history of first or possible secondhand asbestos exposure and symptoms as early as possible.

Diagnosing Sarcomatoid Mesothelioma

Doctors make a sarcomatoid mesothelioma diagnosis using a combination of imaging scans, biopsies and histology tests. Genetic testing is a newer experimental diagnostic technique, and in 2018, a study testing for the BAP1 and MTAP genes was 100% accurate for distinguishing sarcomatoid mesothelioma from fibrous pleuritis.

Imaging studies such as X-rays, CT scans or MRIs reveal abnormalities in the chest, but they do not show specific details such as cell type. Doctors order imaging scans if a patient has a history of asbestos exposure or concerning symptoms.

If your imaging studies suggest cancer, your doctor may refer you for a biopsy where a surgeon collects a small tumor sample for lab testing. Physicians can obtain tumor tissue samples using a needle, but a thoracoscopic procedure under anesthesia is more accurate.

A histologist or pathologist is a specialist who studies cells from tissue samples. After a biopsy, they run immunohistochemistry tests to reveal the cancer cell type and stage. These tests involve staining tumor cells using antibodies that attach to antigens on the tumor.

Misdiagnosing Sarcomatoid Mesothelioma

Mesothelioma is unfortunately often misdiagnosed because signs of the disease mimic other less severe conditions.

Physicians inexperienced with sarcomatoid mesothelioma tend to misdiagnose the disease as other types of thoracic or lung cancer.

Seeking a second opinion from a mesothelioma specialty team is essential for sarcomatoid patients because this group will include pathologists skilled in this diagnosis.

Prognosis for Sarcomatoid Mesothelioma

The life expectancy for patients with sarcomatoid mesothelioma ranges from four to 18 months with treatment. Without treatment, the median survival for patients with sarcomatoid tumors is typically less than six months.

Sarcomatoid cells are notoriously resistant to treatment because of their fibrous nature. Current treatments, however, have helped patients with the lymphohistiocytoid cell subtype survive up to four years, and one patient remained symptom-free for 12 years after diagnosis.

It’s important to note that doctors use past data to make prognosis estimates. As more treatment options become available, the prognosis typically improves. Current survival rate statistics don’t take this most recent data into account.

Each patient’s sarcomatoid mesothelioma prognosis differs based on overall patient health and the stage and location of cancer. Clinical trials offer the best chance at improving prognosis through the newest therapies available at specialized centers.

Sarcomatoid Mesothelioma Treatment

Sarcomatoid mesothelioma treatment options include immunotherapy, chemotherapy, targeted therapy and radiation therapy. Surgeons generally do not operate on patients with sarcomatoid mesothelioma because these cells usually return within a few months of the procedure.

There is currently no cure for sarcomatoid or any other variant of mesothelioma. However, sarcomatoid mesothelioma treatment can improve cancer symptoms, extend survival and increase the quality of life for many patients.

“There are many variants of mesothelioma, sarcomatoid being one of the rarest and potentially trickiest to treat. The Patient Advocates here at The Mesothelioma Center can assist the patient in connecting with a specialist who can successfully diagnose and also craft the best overall treatment plan based on the uniqueness of the patient’s needs.”

Karen Selby, R.N.

Patient Advocate at The Mesothelioma Center

Immunotherapy

Nivolumab and ipilimumab, also known by the brand names Opdivo and Yervoy, are part of a U.S. Food and Drug Administration-approved immunotherapy combination for mesothelioma, including the sarcomatoid cell type.

This drug combination has improved the median overall survival of patients by four months compared to those receiving chemotherapy. It became the new first-line treatment for inoperable mesothelioma in 2020.

Chemotherapy

The standard chemotherapy for malignant pleural mesothelioma patients with any cell type is a combination of pemetrexed (Alimta) plus cisplatin or carboplatin in a first-line setting, meaning it’s best for patients who have had no prior cancer therapy.

In a 2021 research study, pleural mesothelioma patients with sarcomatoid and biphasic cell types treated with first-line chemotherapy had a median overall survival of 15 months.

Targeted Therapy

AZD8186 is an experimental targeted therapy drug that is effective with some cancers when combined with other targeted drugs or chemotherapy. Targeted therapies invade cancer cells without harmful adverse effects throughout the rest of the body, which is often the case with chemotherapy.

Research in mice suggests a combination of AZD8186 and the targeted drug selumetinib may be successful in patients with sarcomatoid malignant mesothelioma. The 2020 trial increased survival without significant toxicity.

Radiation Therapy

Doctors may use radiation therapy for sarcomatoid mesothelioma patients as part of a multimodal treatment plan alongside immunotherapy or chemotherapy.

Radiation therapy is not considered curative for mesothelioma. As a palliative therapy, it can reduce pain and improve the quality of life for patients with painful tumors penetrating the chest wall.

Surgery

A 2020 study published in the journal Translational Lung Cancer Research confirmed that surgery for sarcomatoid mesothelioma is not typically an option for most patients. Sarcomatoid tumors are rigid, widespread and return quickly, making surgery less effective.

Surgeons face a similar challenge for peritoneal mesothelioma tumors that surround vital organs. Patients with epithelioid tumors may live for years after surgery, whereas surgery is less beneficial for sarcomatoid patients who may survive only a few months.

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Common Questions About Sarcomatoid Mesothelioma

Is sarcomatoid a type of mesothelioma?

Sarcomatoid mesothelioma is a cancer variant involving the rarest of three tumor cell types. Other mesothelioma tumor cell types include epithelial and biphasic, which describe the type of cells within a patient’s tumor. Sarcomatoid mesothelioma cancer cells appear long and spindle-shaped, forming diffuse and fibrous tumors throughout the pleura.

What do I need to know about sarcomatoid mesothelioma?

• Sarcomatoid is the most aggressive and fastest spreading mesothelioma cell type and has the lowest average survival rate.
• It makes up 10% to 20% of all mesothelioma cases.
• This cell type is more resistant to treatment than other types.
• However, clinical trials are testing new therapies for sarcomatoid mesothelioma that may be available through your physician.

What is the survival rate for sarcomatoid mesothelioma?

The median overall survival for sarcomatoid mesothelioma patients is 8.6 months. In a 2021 clinical research study, patients with sarcomatoid mesothelioma who received immunotherapy had a median overall survival of 15 months. The median overall survival was 10.7 months for those who received chemotherapy.

How do I find a doctor who treats sarcomatoid mesothelioma?

All mesothelioma doctors have studied sarcomatoid mesothelioma and received training to treat this specific cell type. These specialists know the right treatments and approaches that best control sarcomatoid mesothelioma. They also can connect you to clinical trials designed for patients with this cell type.