Understanding Surgical Margins in Breast Cancer Surgery

If you require a lumpectomy for breast cancer, your surgeon will remove the tumor, as well as some tissue surrounding the tumor. This border of tissue is called the surgical margin. Once removed, it is examined by a pathologist to determine if all the cancer cells in that area are gone and whether further treatment is required.

Understanding Surgical Margins

After your surgeon removes the tumor and the tissue, all of it is sent to the pathology lab, where a pathologist uses a special type of ink to draw a line along the outer edge of the entire tissue sample. Then the sample is sliced into thin sections and examined under a microscope. If cancer cells are found anywhere between the tumor itself and the outer edge of the margin, further surgery may be necessary.

There is no strict guideline for exactly how wide the margin around a tumor should be, though between 1mm and 2mm is typical. A 2016 study indicated that using wider margins does not necessarily prevent local recurrence more effectively than using narrower ones in women who received a lumpectomy followed by radiation.

These three terms are used to describe margins:

  • Negative (or clear) margin: No cancer cells at the outer inked edge of the tissue
  • Positive margin: Cancer cells or tumor extends to the edge of the sample
  • Close margin: Any situation in between negative and positive

When Surgical Margins Contain Cancer

Close margins found after a lumpectomy might require another surgical procedure, called a re-excision. In this case, your surgeon would return to the original site and remove additional tissue to try and get negative margins.

Positive margins may indicate the presence of invasive breast cancer, and you may need to have a mastectomy in order to be sure that all cancer has been removed and to prevent a recurrence. Some women with close margins choose to have a mastectomy to remove the tissue, rather than undergo one or possibly two more surgeries.

If you've had a biopsy, your tumor is small (under 4cm), and your surgical margins are clear, a lumpectomy may be all the breast surgery you need.

Most women receive radiation after a lumpectomy to prevent a recurrence of cancer, even if the margins are clear. If a mastectomy was needed, chemotherapy as well as radiation may be required, depending on the stage and other features of the cancer, including the status of the lymph nodes.

A Word From Verywell

Once you've had a lumpectomy, you'll find out if your surgical margins were negative, positive, or close. This, along with cancer type, stage and lymph node status, will help you and your doctor choose the most effective follow-up treatment for you.

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