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Approximately 20 percent of diagnosed mesotheliomas are biphasic. Biphasic mesothelioma is one of three major classifications and refers to cell type. Cells in mesothelioma tumors may be epithelioid, sarcomatoid, or a mix of the two. A mesothelioma tumor with a mix of the two cell types is known as biphasic. There are other rare cell types as well as several cell sub-types. However, these three account for almost all diagnoses.
Treatment and prognosis for biphasic mesothelioma varies by individual. The more sarcomatoid cells that are present, the more aggressive treatment will be and the worse the prognosis. If there are more epithelial cells, the tumor will be easier to treat, and the prognosis slightly better.
Before treatment can begin, a complete diagnosis is necessary. This will determine the tumor’s cell type and help your medical team determine the right treatment plan.
Histology is the study of microscopic cell structures. When a tumor is discovered through imaging scans, the next step is to perform a biopsy. Cells removed in the biopsy sample will be examined by a pathologist to determine whether they are benign or malignant. He or she will also determine from which type of tissue the tumor cells originated. Mesothelioma cells may originate in the peritoneum, pleura, pericardium, or elsewhere in the body.
Once a diagnosis of mesothelioma has reached this stage, the pathologist will also look at biopsied cells to determine their histological classification, or cell type. At this point, diagnosis will pinpoint the category of epithelioid, sarcomatoid, or biphasic. To be classified as biphasic, the biopsied sample must contain more than ten percent of either epithelioid or sarcomatoid cells. The remaining cells can consist of the other type.
Sarcomatoid and Epithelioid Cells
Biphasic mesotheliomas are tumors that include a mix of these two cell types. Epithelial cells make up tissue in the body that line surfaces of organs, blood vessels, and the interiors of cavities. When these cells become cancerous, it is called a carcinoma.
On the other hand, sarcoma develops from cells that make up bone, fat, muscle, vascular, and connective tissue. Sarcomas are more rare than carcinomas.
Epithelioid mesothelioma cells are easier to treat. They are also less aggressive because they tend to stick together rather than spread. Sarcomatoid cells are more likely to spread to other organs as they adhere less to one another. Epithelioid cells appear as rounded, cube-like shapes. Sarcomatoid cells are spindle shaped and arrange themselves in a disorganized manner. Biphasic tumors could have up to 90 percent of either cell type.
Diagnosis of biphasic mesothelioma is similar to diagnosis of any type of mesothelioma, with a visit to the doctor. Some of the symptoms of biphasic mesothelioma may include chest pain, and difficulty breathing. It may also present as a liver mass and was shown to simulate primary hepatic or secondary tumors. After a medical history and physical exam, the doctor may perform patient scans to create an image of the body’s interior. An X-ray, CT scan, MRI, or PET scan (or combination of these) may be used to determine if are tumors or other abnormal tissues.
If a scan shows nothing abnormal, the next step is a tissue biopsy. In most cases this requires the insertion of a needle to draw fluid or tissue. If the tumor is particularly difficult to reach, a more invasive biopsy may be necessary, usually involving an incision or surgery.
A pathologist then examines the biopsied cells. The sample is stained and then examined under a microscope to determine if cells are malignant or benign. The pathologist will also determine if the cells in the mesothelium or some other tissue. This histological diagnosis is not always accurate. It is often difficult to distinguish mesothelioma cells from other cancer types.
If the pathologist makes a confident mesothelioma diagnosis, he or she will then examine the cells to determine what type they are. If there is a mix of epithelioid and sarcomatoid cells in the sample, the diagnosis will be biphasic mesothelioma.
Treatment for biphasic mesothelioma depends on many factors. One factor is the ratio of epithelial to sarcomatoid cells. If more epithelial cells are present, the cancer is likely to spread slowly to areas near the original tumor. If sarcomatoid cells dominate, the cancer is more likely to be fast-growing and aggressive. Tumor heterogeneity is the major factor limiting the efficiency of treatment options for biphasic mesothelioma.
There are also individual factors to consider. These factors include the patient’s health, tumor location, and how extensive the much metastasis. Surgery is usually only performed for epithelioid mesotheliomas. However, if the biphasic tumor is mostly epithelioid, surgical removal of all or part of the tumor may be part of treatment. Surgery is typically followed by radiation and chemotherapy.
For mostly sarcomatoid biphasic tumors, chemotherapy and radiation are more likely choices for treatment.
As with treatment, prognosis for patients with biphasic mesothelioma is varied. Unfortunately, patients mostly have a poor prognosis. Even with mostly epithelial cells, this cancer type is aggressive and is often not diagnosed until the latter stages of development. Survival rates for biphasic mesothelioma are low. However, patients with biphasic mesothelioma are expected to live longer than those with true sarcomatoid tumors. More epithelial cells present in a biphasic tumor, the longer a patient will be expected to live.
All types of malignant mesothelioma have a strong correlation with regular asbestos exposure. If you were exposed to asbestos and then received a diagnosis of biphasic mesothelioma, you may feel someone else is to blame. Either your employer or the maker of asbestos-containing materials could be at fault for your suffering. You can take advantage of asbestos and mesothelioma trust funds or start a lawsuit if you feel you have a strong case to make. This process can be complicated, but a lawyer with experience in asbestos and mesothelioma cases can help you navigate the process.
Page Medically Reviewed and Edited by Pinar Kanlikilicer, PhD
Dr. Pinar Kanlikilicer has a PhD in Biomedical Engineering. She completed her 5-years of postdoctoral training in the Department of Experimental Therapeutics at MD Anderson Cancer Center. She is currently working in the field of cancer as a research scientist.