Learning About Breast Cancer

Breast cancer is a malignant (muh-LIG-nent) tumor that starts with cells in the breast. Malignant means that the cells are cancerous and may spread to other tissue in the breast. Sometimes the cancer cells spread outside the breast to other parts of the body. This means they metastasize (meh-TASS-ta-size).

Ducts in the breast carry milk to the nipple. Most breast cancers start in the cells that make up the milk ducts. Some breast cancers start in the lobules (glands where breast milk is made).

A breast biopsy is the only way to tell if breast cells are abnormal or cancerous. For a breast biopsy, a doctor removes a small piece of breast tissue. The tissue is looked at under a microscope to check for changes. If the cells are abnormal or cancerous, a biopsy may tell if they are still in one place or if they have started to spread.

Non-Invasive Breast Cancer
A non-invasive breast cancer is a growth of abnormal cells found in the breast. The cells have not spread to other tissue in the breast or other parts of the body.

LCIS (lobular carcinoma in situ)—With LCIS, abnormal cells grow inside the lobules. “In situ” means “in place.” The abnormal cells have stayed in one place. LCIS rarely becomes invasive cancer. But women with LCIS are at higher risk for invasive breast cancer.
DCIS (ductal carcinoma in situ)—With DCIS, abnormal cells grow inside the milk ducts. It is called “in situ” because the abnormal cells have stayed in one place. DCIS is the most common non-invasive breast cancer. There is a chance that DCIS might become invasive cancer later on.

Invasive Breast Cancer
With invasive breast cancer, the abnormal cells have spread beyond the place where they started. Invasive breast cancer can start in the milk ducts or the lobules. But “invasive” means that the cancerous cells have spread to other breast tissue.