Cancer is a renegade system of growth that originates within a patient's body. There are many different types of cancers, but all share one identifying characteristic: unchecked growth that progresses toward limitless expansion. It is difficult to imagine anyone who has not heard of this illness. Many people have been affected because either they or their loved ones or friends are cancer survivors.
Cancer can originate almost anywhere in the body. The National Cancer Institute identifies the four basic types of cancer as:
Carcinomas - the most common types of cancer arise from the cells that cover external and internal body surfaces. Lung, breast, and colon are the most frequent cancers of this type in the United States.
Sarcomas - cancers arising from cells found in the supporting tissues of the body such as bone, cartilage, fat, connective tissue, and muscle.
Lymphomas - cancers that arise in the lymph nodes and tissues of the body's immune system.
Leukemia - cancers of immature blood cells that grow in the bone marrow and tend to accumulate in large numbers in the bloodstream.
Not all tumors are cancerous. There are two different types of tumors:
- Benign tumors aren't cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body.
- Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis.
A malignant tumor is a more serious health problem than a benign tumor because cancer cells can spread to distant parts of the body. For example, a melanoma (a cancer of pigmented cells) arising in the skin can have cells that enter the bloodstream and spread to distant organs such as the liver or brain.
Cancer cells in the liver would be called metastatic melanoma, not liver cancer. Metastases share the name of the original ("primary") tumor.