Sarcomatoid cells are found mainly in the tumors of pleural mesothelioma. Sarcomatoid mesothelioma is the rarest form of the asbestos-related cancer and is considered the least treatable, with a poor prognosis for most patients.

Sarcomatoid Mesothelioma

There are three different types of cells which cause the rare cancer, mesothelioma. Sarcomatoid-type mesothelioma only accounts for 10 to 15 percent of mesothelioma cases. It is a cell type that metastasizes quickly, making it the most aggressive type of mesothelioma.

Sarcomatoid mesothelioma may not develop for decades after asbestos exposure. Over a long period of time, the needle-like asbestos fibers that have lodged in the lungs, peritoneum or other mesothelial layers, will cause inflammation and mutation of the cellular DNA. This causes the sarcoma or soft-tissue cells to begin dividing uncontrollably, forming a tumor.

Sarcomatoid Mesothelioma Characteristics

Rather than solid tumors, sarcomatoid mesothelioma is characterized as disorganized, fibrous and diffuse. The tumors form in nodules, often scattered across the mesothelial layer of the lungs or abdomen. As the cancer progresses, the nodules may grow together in a sheet like mass. Because this mass is spread across a large portion of tissue, it is difficult to remove through surgery and radiation may not be as effective as desired.

In other cases, the tumors are disorganized and loose and may form a hollow or liquid center. The sarcomatoid cells in this type of tumor may break away, infecting the lymph system to be transported to distant parts of the body as metastases. Metastatic cancer results in the growth of new tumors in distant locations such as on the liver, brain, bladder or kidneys. Metastatic cancer is considered to be largely untreatable.


Sarcomatoid mesothelioma is the rarest cell type of mesothelioma and accounts for only about 10 to 15 percent of all mesothelioma cases. It is more common in pleural mesothelioma but may occur in peritoneal mesothelioma as well.


Sarcomatoid cells are “spindle-shaped” with an elongated, large nucleus. In some cases these cells have multiple nuclei and may be harder to differentiate from healthy tissue. Sarcomatoid mesothelioma develops from soft tissue sarcoma cells, once the cells become cancerous, they are known as sarcomatoid.


Unlike other cell types, sarcomatoid mesothelioma cells do not bond or stick together well. They form loose, fibrous and disorganized tumors which may not contain solid centers. Because they are diffuse and not well organized, they may easily spread into the lymph nodes and metastasize to other areas of the body.

Sarcomatoid Mesothelioma Diagnosis

Sarcomatoid cell types make up 10 to 20 percent of pleural mesothelioma cases and 4 percent of peritoneal mesothelioma cases. Sarcomatoid cells are also found in other cancers including bladder, lung, kidney and liver cancers.

Sarcomatoid cells can be similar in appearance to non-cancerous tissue and sarcomatoid mesothelioma may be mis-diagnosed as other disorders such as fibrosarcoma, fibrous pleurisy and metastasized cancers of the kidney or other organs.

In general, symptoms of sarcomatoid mesothelioma will be determined by the location of the tumors.

Pleural sarcomatoid mesothelioma may cause

  • Shortness of breath
  • Difficulty breathing
  • Chest pain
  • Weakness and fatigue
  • Weight loss

Peritoneal sarcomatoid mesothelioma may cause

  • Abdominal pain
  • Swelling of the abdomen
  • Loss of appetite or feeling of “fullness”
  • Nausea

As sarcomatoid cells are difficult to differentiate from other cancer cells and from healthy tissue, microscopic examination must be performed by a pathologist in a procedure known as immunohistochemistry. This procedure uses a type of staining to make certain proteins more visible.

Subtypes of Sarcomatoid Mesothelioma

There are three basic sub-types of sarcomatoid mesothelioma. Determining the sub-type may help to identify what treatment options may be more successful than others.

Transitional Mesothelioma – Cells are plump and spindle shaped and behave in an expected fashion

Lymphohistiocytoid Mesothelioma – Accounts for only 1 percent of the type and contain a number of inflammatory and immune-like cells which are large and spindle shaped.

Desmoplastic Mesothelioma – Accounts for about 5 percent of this type and is difficult to diagnose. Cell formation appears to be pattern less with a long structure containing collagen bundles.


Treatment for mesothelioma is mainly based on the type and location of the cancer, not the type of cell but treatment of sarcomatoid mesothelioma is more difficult, no matter where it is located. Like other forms of mesothelioma, treatment options include surgery, chemotherapy, radiation and newer procedures. Despite the availability of multiple treatment regimens, sarcomatoid mesothelioma is difficult to treat.

Surgery is most commonly used for pleural mesothelioma, however with sarcomatoid cells and tumor formation, removal of tumor tissue may be difficult. As it is disorganized and unpredictable, tumor tissue may be rigidly attached to the chest wall, wrapped around the intestines, have formed a “sheet” of sarcomatoid tumor tissue or may be diffuse and easily fall apart upon removal attempt. In any type of cancer, a single cell that is left behind after treatment may grow into a new tumor.

Radiation may not be an option because of the unpredictable structure of sarcomatoid mesothelioma tumors and it’s similarity to surrounding tissue. This is particularly true if tumor(s) are threatening or invading vital organs including the lungs and heart.

Chemotherapy has not traditionally shown a lot of success in shrinking sarcomatoid tumors but newer types of medication and combination of multiple chemotherapeutic agents may improve the patient’s prognosis.

Newer treatments which are still under investigation as part of a clinical trial may be available. These investigational medications or treatment procedures may help to improve the prognosis of sarcomatoid mesothelioma.

Sarcomatoid mesothelioma, no matter whether Pleural, peritoneal, pericardial or testicular mesothelioma, is aggressive, unpredictable, and fast-spreading. Any patient who is diagnosed with mesothelioma, particularly if cells have been determined to be sarcomatoid-type cells, should seek treatment form a mesothelioma specialist. Mesothelioma is an extremely rare cancer and only a mesothelioma specialist will have the experience and the expertise to treat this challenging disease and produce the best outcome.