(margin) The edge or border of the tissue removed in cancer surgery. The 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. The margin is described as positive or involved when the pathologist finds cancer cells at the edge of the tissue, suggesting that all of the cancer has not been removed.

One of the criteria for assessment of the effectiveness of given surgical procedure in achieving the local control of a neoplasm and the adequacy of tumor removal. It is defined by the tissue plane through which the dissection has been done and the actual or potential neoplastic tissue which has been left outside the boundary of a resected specimen within the patient. There are four types of surgical margins: intracapsular or intralesional, marginal, wide, and radical.

(margins of excision) The edges of tissue removed in a surgery for assessment of the effectiveness of a surgical procedure in achieving the local control of a neoplasm and the adequacy of tumor removal. When the margin is negative or not involved by tumor (e.g., CANCER) it suggests all of the tumor has been removed by the surgery.