In its most general terms, cancer is a word used to describe the occurrence of cells in any part of the body or on the external skin to grow out of control and in a dis-ordered manner. Normal cells are able to regulate their growth and division, but cancer cells do not have this ability. There are many different types of cancer, many of which are more treatable than others, but all forms of cancer share at least one common feature: they are abnormal cells.

Sometimes, different types of cancer consist of very different types of abnormal cells. This is why different types of cancer are treated with different medications and procedures. For example, the treatment for breast cancer is completely different from the treatment a mesothelioma patient receives.

In terms of mesothelioma, a tumor begins to form when the cells on the mesothelium begin to grow abnormally and out of control. Normally, these abnormal cells do not know how to stop dividing and they grow and grow until a lump or a tumor can be seen. Eventually, the tumors begin to inhibit the functioning of the normal cells. When this occurs, a person's body does not work as it should, and the person becomes dangerously ill.

Mesothelioma is a cancer that produces tumors, and when just a few cells from the tumor break away and travel through the blood stream, they can land in another area and begin growing. This is called metastasis, and is an extremely common occurrence with malignant mesothelioma.

The general public is constantly cautioned about what causes an increased risk of developing cancer. In general, risk factors boil down to habits (i.e. smoking and drinking, excessive sun exposure), family history, health conditions, and the environment in which a person works and lives. In the case of mesothelioma, it has been determined that almost every single case is due to the unprotected exposure and inhalation of asbestos particles at any time during a person's life.

A diagnosis of any form of cancer, including mesothelioma, can only be diagnosed by way of a biopsy. For a biopsy, doctor will take a tiny sample of the cells causing a lump, tumor or suspicious group of cells, and look at it under microscope. While tests such as x-rays and other imaging scans can see masses or lumps, they can not determine the type of cells that make up abnormal growths. When a doctor looks at the cells under a microscope, it can be determined if the cells are cancerous, and usually what type of cancer is present.