Sarcomatoid pleural mesothelioma is the most aggressive type of mesothelioma. This type of mesothelioma is formed by sarcomatoid cells and is located in the pleura, or the lining of the lungs. Sarcomatoid is the least common cell type of mesothelioma and can affect treatment and prognosis.
Approximately 10 to 20 percent of all pleural mesothelioma cases are characterized by sarcomatoid cells, which can spread at an alarming rate. This cell type is more resistant to treatment options than other mesothelioma cell types.
Sarcomatoid tumors are also known as sarcomatous, spindled or diffuse malignant fibrous mesothelioma. The tumor cells are haphazardly organized, and they appear spindle-shaped with plump, elongated nuclei.
Sarcomatoid tumors most often form as small nodules scattering the surface of the lung lining. As the nodules grow, they merge to form a sheet-like tumor across the pleura. In rare cases, a single tumor mass may form instead, which is harder to remove surgically if the tumor has grown into the chest wall.
Pleural effusion isn’t as common for this mesothelioma cell type, but can develop in some cases. Pleural effusion is often the cause of initial pleural mesothelioma symptoms, including shortness of breath and chest pain. These symptoms may not be as severe in patients without pleural effusion. Patients with a single tumor mass growing into the chest wall may experience more significant chest pain than patients with sheet-like tumor growth.
All three mesothelioma cell types, sarcomatoid, epithelial and biphasic, can affect treatment and prognosis. If diagnosed with sarcomatoid pleural mesothelioma, a patient may not respond to treatment as well as someone diagnosed with a different cell type, leading to a shorter life expectancy and fewer treatment options. If a sarcomatoid mesothelioma patient is diagnosed in an early stage, treatment options are more effective.
How Is Sarcomatoid Pleural Mesothelioma is Diagnosed?
Diagnosing sarcomatoid pleural mesothelioma is difficult because sarcomatoid tumors often resemble benign and other malignant conditions, and an initial misdiagnosis is possible. Under a microscope, sarcomatoid tissue samples can appear similar to sarcoma tumors and localized tumors of the pleura.
Common misdiagnoses for sarcomatoid pleural mesothelioma include:
- Fibrous pleurisy
- Malignant fibrous histiocytoma
- Metastasized renal cell carcinoma
- Localized fibrous tumors
- Pleural liposarcoma
Diagnosing pleural this type of pleural mesothelioma may also be difficult because symptoms of pleural mesothelioma can mimic symptoms of other, less serious respiratory illnesses, including pneumonia or asthma.
For physicians to accurately diagnose sarcomatoid pleural mesothelioma, they must first visually identify the cancer by taking an imaging test such as a CT scan, MRI or X-ray. Then, to determine the cell type, a tissue sample called a biopsy of the tumor must be taken. Biopsies allow physicians to more closely examine the tumor, but if the tissue sample is too small, it may be hard to determine all of the cell’s features, which could also lead to an initial misdiagnosis.
Immunohistochemistry, a tissue-staining technique, can help differentiate sarcomatoid mesothelioma from other tumors that look similar. This technique uses antibodies, which react to proteins in the tissue sample from a biopsy, to discern cell samples. The reaction is visible under a microscope and can help identify the type of tumor, which can help a physician determine the right course of treatment.
Sarcomatoid pleural mesothelioma tissue generally does not react to the typical antibody used in this technique. Instead, different antibodies such as CAM5.2, WT1, podoplanin and D2-40, will indicate the presence of sarcomatoid cells. These antibodies will also stain negative for other tumors that appear similar to sarcomatoid tumors.
Diagnosing sarcomatoid pleural mesothelioma can also be difficult because there are three variations of sarcomatoid mesothelioma: transitional, lymphohistiocytoid and desmoplastic. Each of these variants consists of different cell structures and characteristics, making it even harder to make a proper and definitive diagnosis.
|Three variations of sarcomatoid mesothelioma:|
|Transitional mesothelioma - has plump, spindle-shaped cells, rather than spindle-shaped cells with plump, elongated nuclei.|
|Lymphohistiocytoid mesothelioma - has large, spindle-shaped cells, and immune and inflammatory cells throughout. This cell subtype accounts for less than 1 percent of all mesothelioma cases.|
|Desmoplastic mesothelioma - is one of the most difficult cell subtypes to diagnose, accounting for about 5 percent of all mesothelioma cases. It is largely characterized by its lack of a pattern. It also consists of some elongated cells and collagen bundles.|
How Sarcomatoid Cells Affect Pleural Mesothelioma Treatment and Prognosis
Given the aggressiveness of sarcomatoid tumors, prognosis for this cell type is not as favorable as other cell types, and there are not as many treatment options available.
Like other cell types, treatment is dependent on the stage of cancer and the location of the tumor. This means that conventional treatment such as surgery, chemotherapy and radiation therapy may be options for those diagnosed with this cell type. Unfortunately, sarcomatoid cells are more resistant to treatment, especially if diagnosed in its later stages.
In particular, sarcomatoid pleural mesothelioma is difficult to treat with surgery, because these tumors typically penetrate the chest wall and can become difficult and more complicated to remove. Unfortunately, chemotherapy also has had limited success in treating sarcomatoid pleural mesothelioma.
There may be hope in a newer drug called selenite, which has so far proven to be a more potent chemotherapy drug for all mesothelioma cell types, including sarcomatoid. Research has shown that selenite combined with doxorubicin, an anthracycline antibiotic, has caused apoptosis, or cell death. But no human studies have been conducted yet. Another chemotherapy drug combination that has produced favorable results in some cases is known as CYVADIC chemotherapy, which incorporates several medications, including cyclophosphamide, vincristine, doxorubicin, also called adriamycin, and dacarbazine, also called DTIC. However, the response rate is usually low, which is why this therapy isn’t commonly used to treat pleural mesothelioma.
Clinical trials for sarcomatoid pleural mesothelioma can be difficult, because it is such a rare diagnosis. However, specialized mesothelioma programs are aimed to improve treatment options and resources for patients.
Alternative and complementary medicines may also be an option, but patients should first consult a mesothelioma specialist before deciding on any course of treatment.