Surgical margin, also known as tumor free margin, free margin, normal skin margin, and normal tissue margin, usually refers to the visible normal tissue or skin margin that is removed with the surgical excision of a tumor, growth, or malignancy.
Surgical margin in a surgery reports define the visible margin or free edge of "normal" tissue seen by the surgeon with the naked eye. Surgical margin as read in a pathology report define the histological measurement of normal or unaffected tissue surrounding the visible tumor under a microscope on a glass mounted histology section. [1] A "narrow" surgical margin implies that the tumor exists very close to the surgical margin, and a "wide" surgical margin implies the tumor exists far from the cut edge or the surgical margin. Narrow surgical margin using the bread loafing technique suggests that residual cancer might be left due to false negative error. A surgeon often will perform a second surgery if a narrow surgical margin is noted on a pathology report.
This determination is made with the full understanding of "false negative error" intrinsic in the bread loafing technique of histology (also known as POMA - a term used by the NCCN)[2]. The higher is the false negative error, the higher is the recurrence rate of a cancer or tumor at the surgical margin. This is due to the misreading of a pathology specimen as being clear of residual tumor, when there is actually residual tumor left where the specimen was not cut and mounted on the histology slide. The "false negative error" is very low in the ccpdma method of histology processing, and can be very high in the bread loafing (POMA) method of histology processing[2]. In the bread loafing method of processing, one will note a high false negative error rate with narrow surgical margin; and one will note a low false negative error with a wide surgical margin[3] Surgical margin has a much less significant effect on the false negative error rate of CCPDMA methods, allowing the surgeon to routinely use very narrow surgical margins (1 to 2 mm for non-melanoma skin cancer).[3]