MultiCare Health System

What is Cancer?

Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. Cancer can spread throughout your body. These abnormal cells sometimes form a mass or lump called a tumor. All tumors are not cancer.

 • Benign tumors do not spread to other parts of the body and are not cancer. They are rarely life threatening and can often be surgically removed.

 • Malignant tumors are cancerous. Cancer spreads when cells break away from the tumor and travel to other parts of your body.

Cancer is not a single disease. There are more than 100 different types of cancers, which are usually named according to the part of the body where they first develop. There are four main types of cancer:

 • Carcinomas are the most common type of cancer. They start in a solid organ such as a lung, breast, prostate, bowel or ovaries.

 • Sarcomas are cancers that start in the muscles, bones and tissues that connect different parts of the body.

 • Leukemias, or blood cancers, are cancers of the white blood cells.

 • Lymphomas are cancers of the lymphatic system, a series of vessels that carry lymph to different parts of the body. Lymph is a watery fluid that contains cells that fight infection and disease.