Cancer is cells growing out of control.

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

Usually, the multiplying cancer cells form a lump called a tumor.

Not all tumors are cancerous. Tumors that are not cancerous are called benign 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.

Normal Cells
Malignant Cells

Defining recurrence

Recurrence is the term used to describe the return of cancer following primary treatment, either at the same site as the original tumor or somewhere else in the body. Breast cancer can recur in the following ways:

Local breast cancer recurrence occurs in the breast where the cancer first started, or in the skin and underlying tissues where the breast used to be. This type of recurrence can happen even if you’ve had a mastectomy. In the soft tissues of the chest, cancer can grow from breast cancer cells close to the skin or behind the breast area, against the muscle of the chest wall. This type of local recurrence is called a chest wall recurrence.

Regional breast cancer recurrence occurs in the lymph nodes near the affected breast. These “regional” lymph nodes include nodes found under the arm (axillary nodes) and those in the chest wall, such as those under the breastbone or under the pectoral muscle at the front of the chest. With regional recurrence, the cancer grows from cells that were present but undetectable at the time of the original surgery, or from cells that recurred in the breast and then later spread to lymph nodes.

Metastatic breast cancer recurrence occurs in other parts of the body, such as lymph nodes at the base of the neck, or in the lung, liver, bone, or brain.

Src: PDR.net