What Is Sarcomatoid Mesothelioma?

Sarcomatoid mesothelioma is a rare mesothelioma cell type. This variant is more resistant to treatment than epithelial or biphasic cells. Sarcomatoid tumor cells are more likely to spread or metastasize to new areas.

Sarcomatoid mesothelioma cells
A pathology stain showing sarcomatoid mesothelioma cells under a microscope.

Sarcomatoid Mesothelioma Facts

  • Their oval, spindle shape characterizes sarcomatoid cells.
  • The center of sarcomatoid cells has one or more enlarged or elongated nuclei.
  • Also called spindle or sarcomatous cells, sarcomatoid cells resemble a sarcoma.
  • Tumors made of sarcomatoid cells can merge to form a fibrous, sheet-like mass.

Sarcomatoid tumors appear fibrous and diffuse throughout the pleura. The pleural membrane surrounds the lungs and lines the chest cavity. There are fewer than 30 documented cases of sarcomatoid peritoneal mesothelioma.

Fibrous and aggressive sarcomatoid cells make this type of mesothelioma challenging to treat. Pathologists identify these 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

Rare sarcomatoid mesothelioma cell subtypes are divided into three categories.

Transitional Mesothelioma: This variant grows and spreads similarly to other sarcomatoid subtypes. It has fat, spindle-shaped cells that help 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.

Sarcomatoid mesothelioma subtypes are rare. They tend to have a higher tendency to metastasize and correlate with a poor prognosis.

The pleura is the most likely location for rare sarcomatoid cell types to develop. 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?

Asbestos is the primary cause of sarcomatoid mesothelioma. Breathing or swallowing asbestos traps fibers in the body. Over time, irritation and inflammation lead to mesothelioma cancer.

Symptoms take 20 to 60 years to appear after asbestos exposure. They often mimic other, more common illnesses. If you have a history of asbestos exposure, speak with your doctor about early screening.

Symptoms of Sarcomatoid Mesothelioma

Sarcomatoid mesothelioma symptoms include nonspecific signs such as cough and shortness of breath.

Common symptoms of sarcomatoid mesothelioma include:
  • Shortness of breath
  • Prolonged hoarseness
  • Persistent cough
  • Coughing up blood
  • Low blood oxygen levels
  • Anemia (low iron)
  • Weight loss and weakness
  • Chest pain or abdominal fullness
  • Lack of appetite, anorexia and nausea
  • Fatigue and extreme tiredness

Patients may also experience chest pain. As the disease progresses, symptoms become more serious. If you have these signs and a history of asbestos exposure, speak with a specialist as soon as possible.

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Diagnosing Sarcomatoid Mesothelioma

Doctors use imaging and biopsies to confirm a sarcomatoid mesothelioma diagnosis. Genetic testing is a newer experimental diagnostic technique. In 2018, researchers studied the BAP1 and MTAP genes as diagnostic tests. The tests were 100% accurate in differentiating sarcomatoid mesothelioma.

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

If your imaging studies suggest cancer, your doctor may refer you for a biopsy. In this procedure, a surgeon collects a small tumor sample for lab testing. Physicians can get tissue samples with a needle, but a thoracoscopy is more accurate.

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

Misdiagnosing Sarcomatoid Mesothelioma

Mesothelioma is often misdiagnosed because the disease mimics less severe conditions.

General oncologists may misdiagnose the disease as other cancers.

Common misdiagnoses include:

  • Pleural liposarcoma
  • Fibrous pleurisy or pleuritis
  • Sarcoma or fibrosarcoma
  • Malignant fibrous histiocytoma (undifferentiated pleomorphic sarcoma)
  • Localized fibrous tumors
  • Metastasized renal cell carcinoma
  • Solitary fibrous tumor of the pleura (hemangiopericytoma)

Seeking a second opinion from a mesothelioma specialty team is essential. Sarcomatoid patients need pathologists skilled in this diagnosis.

Prognosis for Sarcomatoid Mesothelioma

The prognosis is poor for sarcomatoid patients. The life expectancy for sarcomatoid mesothelioma is four to 18 months with treatment. Without treatment, the median survival is less than six months.

Sarcomatoid cells are resistant to treatment because of their fibrous nature. Current therapies have improved lymphohistiocytoid cell subtype survival by up to four years. 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 improves. Current survival rate statistics don’t take this most recent data into account.

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

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Sarcomatoid Mesothelioma Treatment

Sarcomatoid mesothelioma treatment options include immunotherapy, chemotherapy, targeted therapy and radiation therapy. Surgery is less beneficial for sarcomatoid patients because these cells may return.

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

“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 are FDA-approved immunotherapy drugs for sarcomatoid mesothelioma. They are also known by their brand names, Opdivo and Yervoy.

This drug combination has improved patient survival by four months compared to chemotherapy. It became the new first-line treatment for inoperable mesothelioma in 2020.

Chemotherapy

Pemetrexed (Alimta) plus cisplatin or carboplatin is standard chemotherapy for malignant pleural mesothelioma. It is best for patients who have had no prior cancer therapy. Doctors use these drugs in the first-line setting for any cell type.

A 2021 research study assessed survival in sarcomatoid mesothelioma patients. Those treated with first-line chemotherapy had a median survival of 15 months.

Targeted Therapy

AZD8186 is an experimental targeted therapy drug showing effectiveness for some cancers. Targeted therapies treat cancer without harmful effects on the rest of the body.

Research suggests AZD8186 and selumetinib may be successful in treating sarcomatoid cell types. A 2020 clinical trial increased survival without significant toxicity.

Radiation Therapy

Doctors use radiation alongside immunotherapy or chemotherapy in multimodal plans. Radiation therapy is not considered curative for mesothelioma. As a palliative therapy, it can reduce pain and improve the quality of life.

Surgery

A 2020 study in Translational Lung Cancer Research determined surgery was not effective. Sarcomatoid tumors are rigid, widespread and return fast, making surgery less beneficial.

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

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.

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