There are many types of cancer. As with all cancers, affected cells in the body change and grow out of control.

What is cancer?

• Usually, the multiplying cancer cells form a lump called a tumor
• Not all tumors are cancerous. Tumors that are not cancerous are called benign (pronounced beh-NINE) tumors. Cells from benign tumors do not spread to other parts of the body
• Cancerous tumors are called malignant tumors. Sometimes malignant tumor cells can break away from the original, primary tumor and travel through the bloodstream or lymphatic system to other parts of the body. This process is called metastasis (pronounced muh-TASS-tuh-sis)

• Cancer is usually named after the part of the body where it first develops: the primary site. Breast cancer begins in the breast tissue. If it spreads to the lungs, for example, it is still considered breast cancer, not lung cancer
• Doctors use the term "stage" to refer to the extent of cancer within the body. Knowing the stage of your cancer can help you and your doctor determine your best treatment plan.

	Learn more about the stages of breast cancer

 

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Defining breast cancer

Doctors classify breast cancer as early or advanced depending on where the cancer is and how far it has spread.

• Early breast cancer occurs when the cancer is small and contained within the breast without spread to other nearby tissue such as muscle or skin. Early breast cancer may have spread to some lymph nodes in the area, such as those found under the arm.

	Download “Understanding Breast Cancer,” an educational guide for patients and caregivers
	Find out more about treatments for early breast cancer

 

• Advanced breast cancer occurs when the cancer has spread from its original place within the breast to surrounding tissues, such as the skin above or muscle below the breast, or to distant areas of the body. There are two different ways advanced breast cancer can be classified: locally advanced or metastatic:

 

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	Get information about advanced breast cancer treatments
	Learn about the stages of breast cancer