Sarcomatoid mesothelioma, typically, is a type of mesothelioma tumor. Asbestos exposure causes this condition. It is also a rare, aggressive form of cancer accounting for about 10 – 20% of all mesothelioma cases.
Sarcomatoid cells have a spindle, oval shape. Normally, these cells form in separate lesions or nodes. They also metastasize to distant organs quickly and are difficult to treat, with an approximate prognosis of about six months.
What Is Sarcomatoid Mesothelioma?
The three types of primary tumor cells are epithelial cells, Sarcomatoid cells, and biphasic cells. Amon them, sarcomatoid cells are rare and difficult to treat variants. They are also aggressive in nature and can resist treatments.
Asbestos fiber inhalation, in general, causes the mesothelial cells to mutate. Then, they develop and form sarcomatoid mesothelioma.
In fact, the term ‘sarcomatoid’ itself is a general reference for spindle, diffuse or sarcomatous malignant fibrous mesothelioma. Sarcomatoid tumors often merge to form a flat, fibrous mass, wide-spreading on the pleural membrane.
As denoted earlier, these cells spread quickly to other organs. They also have a tendency to resist the treatments and often mimic healthy cells. Hence, treating them is a challenging task.
Pathologists view tissue samples under a special microscope. They identify these cells through their appearance and characteristics such as:
1.) The spindle cells have an oval, long, and spindle shape.
2.) Sometimes, these cells may have multiple nuclei. The nucleus is often elongated and enlarged.
3.) Almost all cases of this disease relate to pleural. In fact, there are less than 30 documented cases, that relate to the parietal peritoneum.
What Are the Symptoms of Sarcomatoid Mesothelioma?
Depending on the location of the disease, the symptoms vary. In some cases, the disease takes about 10 – 50 years to form.
Sarcomatoid cells form along with the lung linings, developing malignant pleural mesothelioma. These cells may also rarely form in the abdominal linings, causing sarcomatoid peritoneal mesothelioma
Common symptoms of sarcomatoid mesothelioma include the following:
Dyspnea (difficulty in breathing)
Abdominal or chest pain
Vomiting and Nausea
Excess fluid in abdomen or lungs
Shortness of breath
In fact, these cells have a tendency to spread faster than other cells. Therefore, the associated symptoms worsen faster, deteriorating the patients’ health.
How Diagnosing of Sarcomatoid Mesothelioma is Done?
In diagnosing process, it is important to identify the mesothelioma cell type accurately. The sarcomatoid cells are rare and resemble other healthy cells in appearance. So, it becomes a challenging task to identify sarcomatoid mesothelioma in the first place.
Generally, the medical experts, begin the diagnosis with image tests including CT scan and X-ray. This helps them to identify excess fluids or visible tumors in the chest cavity. If they find any abnormalities, they may order a blood test to identify the biomarkers.
After that, they may order a biopsy to accurately diagnose sarcomatoid mesothelioma. They may also use tissue biopsy and analysis methods like immunohistochemistry to determine the cell type.
Finally, the pathologists confirm the cell type, its nature (malignant and benign), stage, and prognosis through immunohistochemical stains.
Various immunohistochemical markers can show mesothelioma. According to some studies, if the stains have D2-40 and calretinin (proteins), with pancytokeratin (antibody) combination, they accurately denote sarcomatoid mesothelioma.
In some cases, the tumors may have both sarcomatoid cells and epithelioid cells. Such cases are referred to as biphasic mesothelioma. Therefore, the medical experts may have to process multiple biopsies and additional tests for precise determination.
Sometimes, physicians who do not have experience treating sarcomatoid mesothelioma may tend to misdiagnose. They may mistake it for other types of cancers such as lung cancer or thoracic cancer.
Common misdiagnoses include:
Pleuritis or Fibrous pleurisy
Localized fibrous tumors
Fibrosarcoma or Sarcoma
Undifferentiated pleomorphic sarcoma (also called Malignant fibrous histiocytoma)
Hemangiopericytoma (pleural Solitary fibrous tumor)
Renal cell carcinoma (Metastasized)
What Are the Rare Sub-Types of Sarcomatoid Cells?
There are also some rare subtypes of Sarcomatoid cells that exist. These cells often have a poor prognosis and more aggressive metastasis. Therefore, they are more difficult to treat and have limited treatment options.
Desmoplastic mesothelioma – In most cases, these cells do not have defined patterns. These cells most commonly develop along with the lung linings (pleura). However, they also have been reported forming in testicles (testes) and linings of peritoneal cavities (abdomen) in a few cases.
Desmoplastic mesothelioma accounts for around 5% of mesothelioma cases. According to some studies, infected patients have about 3.8 months of median life expectancy.
Lymphohistiocytoid mesothelioma – Of all diagnoses, these rare cells account only for less than a percent. Typically, these cells form in pleura. Sometimes, the tumors may have multiple cells including immune cells and epithelial cells. On average, the patients have about 2 – 20 months of survival time.
Transitional mesothelioma – Like other subtypes, these cells develop in the pleura. However, they appear in a distinct plump spindle shape. Sometimes, they have a close resemblance to epithelial cells.
In such cases, diagnosis becomes very challenging. The tumors of this subtype have been rarely reported, with only a small number of cases.
What is Sarcomatoid Mesothelioma Prognosis?
Generally, the prognosis of this cell is poor or least favorable compared to other cells. Although some studies indicate 1 -28 months life expectancies, most of the patients survive no more than 6 months on average.
The prognosis also depends on the specific subtype of the cell, its stage of development, patients’ overall health, age, and gender.
If sarcomatoid cells dominate biphasic mesothelioma, the patients would show a poor prognosis. They also have about 12 months of life expectancy. Moreover, if these cells constitute in excess of 10% in a tumor, patients may have very limited options on treatment.
How To Treat Sarcomatoid Mesothelioma?
According to some studies results, sarcomatoid cells can resist several standard therapies. They also spread quickly to other parts of the body. Hence, treating them is a challenging task.
The first treatment line for sarcomatoid mesothelioma is Chemotherapy. In spite of the resistance of the cells, this treatment may extend the survival times in some patients.
One study, between 2000 – 2014, investigated 137 patients suffering from pleural sarcomatoid mesothelioma. Researchers found the following:
1.) Chemotherapy slowed progression or stopped the disease in 19 patients, who received it as their first – line of treatment.
2.) Sarcomatoid patients showed a response rate of 13.9%. However, the same across all other mesothelioma types is 21.9%.
In clinical trials, Immunotherapy treatments have also proven their effectiveness. Some early studies indicate this may be a good option for those patients who previously received chemotherapy treatments.
According to some other early evidence, sarcomatoid mesothelioma may respond to immunotherapy well compared to other cells. In some cases, the doctors may apply radiation therapy also. However, experts often use it as a palliative treatment.
In any case, researchers continue to study the possible combination treatments associated with sarcomatoid mesothelioma cases. The goal is to increase life expectancy and also to provide better treatment options.