Types of Mesothelioma

In general, mesothelioma is a rare form of cancer. Different types of mesothelioma are distinguished between by where the cancer is growing.

About 75% of mesotheliomas start in the chest cavity. They are known as pleural mesotheliomas. Another 10% to 20% begin in the abdomen. These are called peritoneal mesotheliomas. Pericardial mesotheliomas start in the cavity around the heart and are very rare. The covering layer of the testicles is actually an outpouching of peritoneum into the scrotum. Mesotheliomas that affect this covering of the testicles can occur but are quite rare.

It is important not to confuse malignant mesothelioma with benign tumors that also start in the mesothelium. The mesothelium of certain female and male reproductive organs may develop a type of benign tumor called an adenomatoid tumor. In men, this non-cancerous tumor often starts in the epididymis (a small collection of ducts that carry sperm cells out of the testicle). In women, this tumor may begin in the fallopian tubes (tubes that carry eggs from the ovaries to the uterus or womb). Another non-cancerous tumor that may begin in mesothelium near female reproductive organs is called benign cystic mesothelioma.

All three of these forms of mesothelioma are caused by asbestos. Asbestos is a naturally occurring fibrous mineral that was discovered around the 1860s. Due to its highly useful property of being fireproof, asbestos was used greatly in construction in the 1920s, 1930s and 1940s. It was not until the early 1960s when the severe health hazards that asbestos causes were discovered, that asbestos stopped being used.

When exposed to asbestos with insufficient protection a person will breathe in tiny asbestos fibres which are suspended in the air. These fibres pass into the respiratory system until they become lodged in the lining of the lungs. Over time, an accumulation of these asbestos fibres in the lungs can cause pleural mesothelioma. Asbestos fibres may also pass into the lymphatic system and be transported to either the lining of the abdomen or the tissue surrounding the heart. This may cause either peritoneal mesothelioma or pericardial mesothelioma.