Key Points about Sarcomatoid Mesothelioma
- Sarcomatoid is the least common of the major mesothelioma cell types, accounting for 10 to 20% of cases.
- The median survival is around 6 months.
- Mesothelioma metastases to major organs are common.
- The most common treatment approach is palliative care.
Sarcomatoid mesothelioma cells are most often found in pleural mesothelioma. Sarcomatoid mesothelioma is the least common of the major cell types, usually seen in about 10% to 20% of patients, and is considered to have the least favorable prognosis as it’s the most difficult to treat. It is also known as sarcomatous, diffuse malignant fibrous, and spindled mesothelioma.
Sarcomatoid Cell Characteristics
- Spindle-shaped cells
- Enlarged, elongated nucleus
- Sometimes have multiple nuclei
- Difficult to distinguish from healthy cells
- Able to spread quicker than other cell types
This cell type is referred to as sarcomatoid because it shares some characteristics with sarcomas, which are malignant diseases that have their origins from another major cell line, the mesenchymal type. Their appearance under the microscope is also referred to as spindle shaped.
In general, sarcomatoid mesothelioma has a more aggressive growth rate compared to the epithelioid form, and the cells tend not to clump together as do epithelioid cells. This enables greater cancer cell mobility, a tendency to spread over large areas, and the ability to penetrate into the blood or lymph streams resulting in a greater risk of metastasis. Metastases may be to the opposite side of the chest, or to more distant body sites including liver, kidneys, thyroid and adrenal glands, and, rarely, the brain and central nervous system.
Sarcomatoid Cell Mesothelioma Has Three Subtypes
- Transitional — This subtype is a plump, spindle-shaped cell that behaves like standard sarcomatoid cell types.
- Lymphohistiocytoid — This cell is large and spindle-shaped and makes up less than 1% of all mesothelioma cases.
- Desmoplastic — The desmoplastic cell type is patternless and extremely difficult to diagnose. It accounts for roughly 5% of all mesothelioma cases.
Sarcomatoid Mesothelioma is Difficult to Diagnose
It can be a challenge to conclusively diagnose sarcomatoid mesothelioma because of its similarity to other malignant sarcomas. Sarcomatoid mesothelioma can be difficult to distinguish from several benign inflammatory disorders and sarcomas such as:
- Fibrous pleurisy
- Metastasized renal cell carcinoma
- Localized fibrous tumors
- Malignant fibrous histiocytoma
- Pleural liposarcoma
Sarcomatoid mesothelioma is distinguished from other chest and lung tumors by examining the malignant cells in the laboratory. Doctors may first order imaging tests, but to determine the cell type, a biopsy is required. Symptoms vary depending on if the sarcomatoid cells are in the pleura or peritoneum.
- Weight loss
- Difficulty breathing
- Shortness of breath
- Abdominal pain
- Loss of appetite
Treatment Options Are Limited For This Aggressive Cell Type
The treatment options for sarcomatoid mesothelioma are quite limited. It is the most aggressive cell type and while the traditional treatments are options, surgery can be especially challenging. A sarcomatoid tumor is very difficult to remove from the chest wall in pleural mesothelioma. In peritoneal mesothelioma, the tumor envelops the intestine, again making it difficult to resect.
- Surgery — Radical surgery with curative intent results in, at best, a marginal benefit. Given the risks of surgical complications and the impact on quality of life after major surgery, an extensive surgical procedure is not considered an advisable option for most patients with sarcomatoid mesothelioma.
- Chemotherapy — Chemotherapy has been shown to have little to no effect on the survival of sarcomatoid patients.
- Radiation & Palliative Therapy — Palliative therapy to manage symptoms is often the recommended approach. Palliative treatment may include radiation therapy to reduce tumor size along with other measures to improve breathing and provide comfort and pain control. Limited surgical procedures such as pleurodesis or drainage of pleural effusions may also be considered if likely to provide greater patient comfort or relieve labored or painful breathing.
Prognosis Depends on Multiple Factors
The majority of patients with sarcomatoid mesothelioma survive between 4-6 months regardless of the type of therapy, and approximately 10% survive beyond 1 year. There have, however, been mesothelioma sarcomatoid patients who live beyond 5 years.
A perspective on patient outcomes was provided in a recent comparative study that examined the median survival of patients with epithelioid or sarcomatoid mesothelioma according to tumor stage and whether radical surgery was performed. The findings suggest that when patient outcomes are grouped according to both cell type and stage, the median survival of patients with the sarcomatoid cell type is similar in stages I, II, and III, and were also nearly identical for those who did or did not undergo surgery. This was contrasted with the well-described benefit of surgery for patients with the epithelioid form, although the effect of stage level in this study was modest.
Other studies have shown that patients with sarcomatoid mesothelioma treated with chemotherapy or trimodal therapy have a median survival of 6 months.