Margins of Resection

When you have a lumpectomy, resection, excisional biopsy, or mastectomy, a pathologist examines the tumor removed from your breast. The piece of tissue that was removed, or the whole breast if you had a mastectomy, is first rolled in a special ink, so that doctors can always tell what is the outer edge. Knowing where that edge is becomes an essential part of choosing the best surgery and radiation to treat the breast cancer.

The pathologist checks to make sure the edges of the tissue are free of cancer cells. This indicates whether all of the cancer has been removed. The pathologist also measures how far in from the edge cancer cells do occur.

Negative and positive "margins" or "margins of resection" (the distance between the tumor and the edge of the tissue)

A Cancer cells

B Normal tissue

C Ink marking the edge

Doctors use the term "margins" or "margins of resection" to refer to the distance between the tumor and the edge of the tissue. You can think of this as the margin of white space on a printed page that separates words from the edge of the paper. The margins are measured on all six sides: front and back, top and bottom, left and right.

Seeing how close cancer cells are to the edge of the removed tissue helps your doctor make the right treatment decisions. This is particularly important if a decision has to be made about additional surgery—re-excision before radiation versus mastectomy. Find out more about clean margins and radiation therapy.

The information your doctor gathers about a tumor's margins is important for treatment but does not usually influence your prognosis (likelihood of recovery without metastasis or recurrence).

Understanding the margins

The margins of a tumor are described by one of three labels, depending upon what the pathologist sees under the microscope:

• Positive margins: Cancer cells extend out to the edge of the tissue, where the ink is.
• Negative margins: No cancer cells are found in the ink.
• Close margins: Any situation that falls between positive and negative is considered "close."

The definition of "negative margins" varies from one hospital to another. In some places, if there is even one normal cell between the ink and the cancer cells, this is considered a negative margin. In other places, the pathologist will require at least two millimeters of tissue without cancer cells between the ink and the tumor before using the category "negative margins."

You may want to ask your doctor whether your margins were positive, negative, or close, and how negative is defined by your medical team.

More information about treatment options related to particular margins of resection.