Biphasic Mesothelioma, cell types involving 20 to 40 percent of all mesothelioma cases, are epithelioid and sarcomatoid cells hence also called Mixed Mesothelioma.
Mesothelioma is a rare but highly aggressive form of cancer that affects the mesothelium – the thin lining of tissue that surrounds the lungs, heart, and other organs. It is almost always caused by exposure to asbestos. When asbestos fibers enter the airway, they can get lodged in the deepest part of a person’s lungs. There, they can damage sensitive lung tissues and travel to the mesothelium that surrounds the lungs and the pleura – the small body cavity that sits between the lungs and the ribcage. Once in the pleura, asbestos fibers are extremely difficult to remove, and they cause damage in the cells of the pleural mesothelium.
The common theme behind all cancers is mutation. If a cell is exposed to the right amounts of a carcinogen (cancer causing agent), the DNA in its nucleus will be mutated. The mutations that the carcinogen induce will either push the cells along a cancer pathway or will take away the various safeguards that the cell has in place to prevent it from becoming abnormal. In the case of mesothelioma, asbestos fibers are inducing DNA damage and mutation which cause the cells of the mesothelium to start dividing in an unorganized and rapid fashion. This uncontrolled growth results in a deadly tumor.
Biphasic mesothelioma is a type of mesothelioma that carries a particularly poor prognosis. The term “biphasic” refers to the type of cells that make up the cancer. Other types of mesothelioma include epithelioid mesothelioma and sarcomatoid mesothelioma. A team of doctors and pathologists can gather cells from a mesothelioma patient and run a variety of tests on them to determine precisely which type of mesothelioma they are dealing with, and thus what the patient’s prognosis is. Among other factors, they look at the basic size and shape of the cells to help determine which of the three types of mesothelioma they are dealing with.
Epithelioid mesothelioma cells are relatively uniform in their tubular shape and have a distinct cell nucleus. They may be shaped like cubes or multi-sided boxes. This type of cell is the most common, and is responsible for around 50% to 70% of all malignant mesothelioma cases.
Sarcomatoid mesothelioma cells are much more oval-shaped than epithelioid mesothelioma cells. They are more irregular, and the nucleus of each cell is sometimes very difficult to see. This is the rarest mesothelioma cell type, accounting for only around 10% to 15% of all malignant mesothelioma.
Biphasic mesothelioma cells do not have a unique cellular structure. They appear to be somewhere in the middle of epithelioid and sarcomatoid. About 20% to 40% of mesothelioma cases involve biphasic cells. They can appear as intermixed epithelioid and sarcomatoid cells, specific but separate groupings of the two types, or in transitional area between the two.
The three cell types are all treated in the same way. However, they all have different chemical properties, so there might be more specific treatments in the future that are more effective for each cell type. For now, the only physiological difference between the three is that they carry different prognoses. Epithelioid cancer has an average survival time of 8.5 months, sarcomatoid cancers have an average survival time of 7 months, and biphasic cancers have the lowest average survival time of only 6 months.