The Who, What, Where, When and Sometimes, Why.

Assessing Margins after Breast Surgery

What is a margin?

When breast cancer is surgically removed (during a surgical biopsy, lumpectomy or mastectomy), a rim of normal tissue surrounding the tumor is also removed. This rim is called a margin.

Margins help show whether or not all of the tumor was removed.

Learn about mastectomy and tumor margins.

Assessing margins after a lumpectomy or surgical biopsy

A pathologist studies the tissue removed during surgery under a microscope and determines whether or not the margins contain cancer cells.

Negative (also called clean, not involved or clear) margins

  • The margins do not contain cancer cells. (There’s only normal tissue at the edges of the tissue removed from the breast.)
  • In most cases, no more surgery is needed.

Positive (also called involved) margins

  • The margins contain cancer cells.
  • More surgery may be needed to get negative margins. (Discuss this with your surgeon.)
  • Sometimes it’s not possible or necessary to get negative margins due to the tumor location (for example, if it’s at the chest wall or right under the skin).

Close margins

  • The cancer cells approach, but don’t touch the edge of the breast tissue removed.
  • More surgery may or may not be needed, especially with ductal carcinoma in situ (DCIS). (Discuss this with your surgeon.)
  • To further ensure the entire tumor was removed, the removed breast tissue may be X-rayed. This is useful when microcalcifications were found on a mammogram and are related to the cancer. Depending on the results of the X-ray, more tissue may be removed at the time of the surgery.
  • If microcalcifications were found on a mammogram before surgery, another mammogram may be done after surgery to ensure all the microcalcifications were removed.

Read Komen advocate Peggy Johnson’s blog on her involvement in an expert panel’s recommendations on assessing margins.

When will I get my results?

You should get your results about a week after surgery.

Mastectomy and tumor margins

With a mastectomy, the whole breast is removed during surgery. Whether the margins contain cancer cells doesn’t usually affect your treatment.

However, in rare cases after a mastectomy, the deep margin (the margin closest to the chest wall) contains cancer cells. In these cases, more surgery and/or radiation therapy may be recommended.

With a nipple-sparing mastectomy, whether or not the nipple margin (the margin closest to the nipple) contains cancer cells can affect treatment. If the nipple margin contains cancer cells, more surgery and/or radiation therapy may be recommended.


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Fact Sheet

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