A resection margin or surgical margin is the margin of apparently non-tumorous tissue around a tumor that has been surgically removed, called 'resected', in surgical oncology. The resection is an attempt to remove a cancer tumor so that no portion of the malignant growth extends past the edges or margin of the removed tumor and surrounding tissue. These are retained after the surgery and examined microscopically by a pathologist to see if the margin is indeed free from tumor cells. If cancerous cells are found at the edges the operation is much less likely to achieve the desired results. A resection margin or surgical margin is the margin of apparently non-tumorous tissue around a tumor that has been surgically removed, called 'resected', in surgical oncology. The resection is an attempt to remove a cancer tumor so that no portion of the malignant growth extends past the edges or margin of the removed tumor and surrounding tissue. These are retained after the surgery and examined microscopically by a pathologist to see if the margin is indeed free from tumor cells. If cancerous cells are found at the edges the operation is much less likely to achieve the desired results.