The Basics of Breast Cancer Staging

Organization: Author:
Homayoon Sanati, M.D., medical director, MemorialCare Breast Center, Long Beach Memorial
Live Healthy Topics:
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In 2015, the American Cancer Society estimated that more than 230,000 new cases of breast cancer would be diagnosed among women in the United States. Most Americans have had a family member or close friend diagnosed with breast cancer. While it has become a common occurrence, many people do not understand that there are different stages of breast cancer.

After a woman has been diagnosed with breast cancer, MemorialCare Breast Center physicians will determine if it has spread throughout the body and how far. Staging helps determine the severity of the cancer and gives doctors more insight on how to treat it.

When staging, MemorialCare Breast Center doctors must determine:

  • If the cancer is invasive or non-invasive.
  • The size of the tumor and if it has moved into nearby areas of the body.
  • If the cancer has spread to lymph nodes, and if so, how many.
  • If the cancer has spread throughout the body.

The staging starts at stage 0, also called carcinoma in situ. After stage 0, the stages range from I (1) to IV (4). Some stages are divided even further. Essentially, the lower the stage, the less the cancer has spread throughout the body. A higher number means a more aggressive and advanced cancer. Here are some basic definitions:

  • Stage 0
    • The cancer has not spread to the lymph nodes nor the body.
  • Stage I
    • The tumor is 2cm or less and either has not spread or has spread to 1-3 lymph nodes.
    • Stage I can be broken into A and B categories.
  • Stage II
    • The tumor is between 2 cm and 5 cm.
    • Stage II can be broken into A and B categories based on if the cancer spread and, if so, how much it has spread.
  • Stage III
    • The tumor can be 5cm or more.
    • Stage III is broken into A, B and C categories.
  • Stage IV
    • The tumor can be any size.
    • It may or may not spread to nearby lymph nodes.
    • Stage IV cancers will have spread to distant organs or lymph nodes away from the breast. The most common areas are the bones, liver, brain or lungs.

Staging can be based on a physical exam, biopsy, imaging tests and surgery. If a person is unsure of the exact meaning of their stage, they should talk with their oncologists.

The best way to prevent cancer is through routine screening mammograms. The Breast Center, part of the MemorialCare Todd Cancer Institute at Long Beach Medical Center, performs more than 30,000 breast imaging tests each year. Call 800-MEMORIAL to schedule a mammogram today.