Resection margin

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 (called "negative"). If cancerous cells are found at the edges (called "positive") the operation is much less likely to achieve the desired results. The size of the margin is an important issue in areas that are functionally important (i.e., large vessels like the aorta or vital organs) or in areas for which the extent of surgery is minimized due to aesthetic concerns (i.e., melanoma of the face or squamous cell carcinoma of the penis). The desired size of margin around the tumour can vary. In resections for breast cancer, there appears to be a difference between European and American radiation oncologists, with the former preferring larger margins of over 5 mm. Residual tumour at the primary site after treatment (it does not address the surgical margin as commonly believed) is classified by the pathologist as (AJCC 8th Edition): R0 - no cancer cells seen microscopically at the primary tumour site. R1 - cancer cells present microscopically at the primary tumour site. R2 - Macroscopic residual tumour at primary cancer site or regional lymph nodes. It does not include metastatic disease identified but not sampled at the time of surgery. The Margin Status following tumour resection (AJCC 8th Edition): Negative margin: No tumour at the margin. Microscopic positive margin: Tumour identified microscopically at the margin. Macroscopic positive margin: Tumour identified grossly at the margin. Margin not assessed.