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 percent of all cases are strictly sarcomatoid, though sarcomatoid cells are also found in biphasic mesothelioma.
What is Sarcomatoid Mesothelioma?
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.
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 percent of all mesothelioma cases, a situation 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 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 bone.
Exceedingly rare, this mesothelioma cell-type is made of bone cells.
These spindle cells are from cartilage.
Sarcomatoid Mesothelioma Incidence, Prognosis and Survival Rates
There are many factors working against sarcomatoid mesothelioma patients. It is hard to diagnose correctly, and is frequently diagnosed late. Furthermore, this type of mesothelioma is more likely to metastasize (spread) than other cell types, making it even more deadly.
All of these factors contribute to the fact that most patients live at most 6 months after diagnosis, though some live longer. Some patients have lived 5 years or longer – but they are very few.
- In most studies, female mesothelioma patients have longer rates of survival than males.
- Younger mesothelioma patients tend to have a better prognosis than older patients.
- If the cancer spreads before it is diagnosed, the prognosis is typically poor.
- Histology refers to the cancer cell type. Mesothelioma patients with sarcomatoid cells have a worse prognosis than those with epithelioid or biphasic cell types.
- Earlier stages of mesothelioma (Stage 1 and 2) have a better prognosis than later stages (Stage 3 and 4).
Because most incidences of mesothelioma are caused by asbestos exposure, the length and amount of exposure will contribute to the aggressiveness of the disease.
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
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.
- Difficulty breathing
- Chest pain
- Poor sleep
- Easily tired
- Fluid in lungs (pleural effusion)
- Unintended weight-loss
- Loss of hunger
- Peritoneal effusion (swelling in the abdomen)
- Abdominal pain
- Constipation or blockage
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.
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
Generally, mesothelioma is most successful treated using surgery along with chemotherapy and radiation – an approach known as multimodal treatment. Sarcomatoid mesothelioma, however, makes treatment very difficult.
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.
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.
Resources Available for Mesothelioma Patients
- Request a Free Sarcomatoid Mesothelioma Treatment Guide
- Connect with Top Sarcomatoid Mesothelioma Doctors
- Locate the Nearest Comprehensive Cancer Center
Connect with Mesothelioma Experts
If you or a family member has been diagnosed with sarcomatoid mesothelioma, or any other mesothelioma cell type, you may have questions about the diagnosis, treatment options, how to pay for therapy, or other related issues. Don’t hesitate to connect with an expert who can explain what your diagnosis means, and who can provide additional guidance to help you and your family deal with this difficult disease.
Grégoire M. What’s the place of immunotherapy in malignant mesothelioma treatments? Cell Adhesion & Migration. 2010;4(1):153-161.
Khalidi HS, Medeiros LJ, Battifora H. An Often Misdiagnosed Variant of Sarcomatoid Malignant Mesothelioma. American Journal of Clinical Pathology. 2000;113:649-654. doi: 10.1309/7ECY-KN61-PP1M-52EB
Kim K-C, Vo H-P. Localized malignant pleural sarcomatoid mesothelioma misdiagnosed as benign localized fibrous tumor. Journal of Thoracic Disease. 2016;8(6):E379-E384. doi: 10.21037/jtd.2016.03.92
Klebe S, Mahar A, Henderson DW, et al. Malignant mesothelioma with heterologous elements: clinicopathological correlation of 27 cases and literature review. Modern Pathology. 2008;21:1084–1094; doi: 10.1038/modpathol.2008.125
Kim O, Krausz T. Differentiating Sarcomas from Mesotheliomas. Malignant Mesothelioma. New York, NY: Springer Science+Business Media; 2005:527-542.
Malignant Mesothelioma Treatment (PDQ®). National Cancer Institute. http://www.cancer.gov/types/mesothelioma/hp/mesothelioma-treatment-pdq#section/_3 Published August 7, 2015. Accessed September 7, 2016.
Mesothelioma. Mayo Clinic. http://www.mayoclinic.org/diseases-conditions/mesothelioma/basics/definition/con-20026157
Nakao M, Hishida T, Ishii G, et al. Malignant pleural mesothelioma with osteosarcomatous differentiation: characteristic bone scintigraphy findings associated with enhanced tumorous osteogenesis. European Journal of Cardio-Thoracic Surgery. 2011;39(3):421. doi: 10.1016/j.ejcts.2010.06.008
Powers A, Carbone M. Diagnosis of Synovial Sarcoma of the Pleura and Differentiation from Malignant Mesothelioma. New York, NY: Springer Science+Business Media; 2005:543-554.