Defining Cancer
Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Sometimes, abnormal or damaged cells grow and multiply when they shouldn’t. These cells may form tumors, which are lumps of tissue. Tumors can be cancerous or benign. Cancerous tumors spread into, or invade, nearby tissues and can travel to distant places in the body to form new tumors. Benign tumors do not spread into, or invade, nearby tissues.
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How Does it Spread?
A cancer that has spread from the place where it first formed to another place in the body is called metastatic cancer. The process by which cancer cells spread to other parts of the body is called metastasis. In metastasis, cancer cells break away from where they first formed and form new tumors in other parts of the body. Under a microscope, metastatic cancer cells generally look the same as cells of the original cancer.
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Types of Cancer
There are more than 100 types of cancer. Types of cancer are usually named for the organs or tissues where the cancers form. For example, lung cancer starts in the lung, and brain cancer starts in the brain. Cancers also may be described by the type of cell that formed them, such as an epithelial cell or a squamous cell. A few examples of types of cancers include carcinomas, sarcomas, leukemias, lymphomas, and melanomas.
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