What do positive and negative margins mean on a pathology report?

On a pathology report, a margin is the edge of the tissue that has been removed by surgery. According to the National Cancer Institute, the pathologist checks whether abnormal cells are found at these edges.

A margin is described as negative (or "clean") when the pathologist finds no cancer cells at the edge of the tissue, suggesting that all of the cancer has been removed. A margin is described as positive (or "involved") when the pathologist finds cancer cells at the edge of the tissue, suggesting that some of the cancer has not been removed.

The report may also describe lymph nodes. Lymph nodes are called positive if they have cancer cells and negative if they do not.

Margin and lymph node status are part of the microscopic description on the report, and they are summarized in the diagnosis section along with the cancer type, tumor grade, and stage.

A healthcare team can explain what the margin findings mean for a specific situation and whether any further treatment is recommended.