Cancer Overview

Cancer is a disease that begins in your cells.

Cells are the building blocks that form tissues. Tissues are what make up your organs – such as your lungs, bladder, heart and brain.

In a healthy body, cells grow and divide to form new cells as the body needs them. When cells grow old, they die.

Sometimes this normal process changes. New cells form when the body does not need them, and old cells do not die when they should.

These extra cells can form a mass of tissue called a tumor.

Two Kinds of Tumors

Tumors can be either benign (not cancer) or malignant (cancer).

Benign tumors are characterized by the following:

  • They are rarely life-threatening.
  • They generally can be removed, and they usually do not grow back.
  • They do not invade the tissues around them.
  • They do not spread to other parts of the body.

Malignant tumors are characterized by the following:

  • Malignant tumors may be life-threatening.
  • Malignant tumors often can be removed, but sometimes they grow back.
  • Cells from malignant tumors can invade and damage nearby tissues and organs by spreading to other parts of the body.


The spread of cancer is called metastasis.

Cancer cells spread by breaking away from the original (primary) tumor and entering the bloodstream or lymphatic system.

The cells can invade other organs, forming new tumors that damage these organs.

Most cancers are named for where they start in the body. For example, lung cancer starts in the lung, and breast cancer starts in the breast. Lymphoma is a form of cancer that starts in the lymphatic system. And leukemia is cancer that starts in white blood cells (leukocytes).

When cancer spreads and forms a new tumor in another part of the body, the new tumor has the same kind of abnormal cells that started elsewhere in the body.

For example, if prostate cancer spreads to the bones, the cancer cells in the bones are actually prostate cancer cells. The disease is metastatic prostate cancer, not bone cancer. For that reason, it is treated as prostate cancer, not bone cancer.

Physicians sometimes call the new tumor "distant" or metastatic disease.

Source: Premier Health Community Wellness Affiliate - Premier Community Health

Content Updated: September 6, 2013

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