Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 31

Despite histopathology universally being used to assess the completeness of surgical margins, the methods of sectioning to evaluate the completeness of margins may vary. The most common method is to perform four complete radial sections. These represent cranial, caudal, dorsal, and ventral portions of the submitted specimen. Unless the surgeon uses tissue ink to identify the surgical margin, it may be difficult for the pathologist to determine whether any one of these sections represents a surgical margin or a trimming artifact. Tissue inking improves the likelihood that the standard sections evaluated do indeed represent true surgical margins; however, in the case of radial sectioning, the area of margin examined represents only a small percentage of the actual surgical margin surface. Several reports document the fact that with more sections, there is a higher likelihood of finding a positive margin. Comprehensive margin evaluation of a 1 cm cutaneous malignancy is estimated to require greater than 4000 sections, making this an impractical means of assessing margin completeness. Tangential sectioning is an alternative method to evaluate surgical margins. Tangential sections are taken parallel to the inked edge, and represent a potentially more sensitive method to detect residual tumor at the margin because they evaluate a greater percentage of the total margin. In humans, significant differences were noted in margin reporting outcomes when tangential sectioning was compared with radial methods. The disadvantage to tangential sectioning is that it does not allow for quantification of the histologically tumor‐free distance and lacks contextual reference to the primary tumor. In one recently reported study in the veterinary literature (Dores et al. 2018), tangential sections detected a significantly higher proportion of positive margins as compared with radial sections in resected mast cell tumors. In this study, radial sections incorrectly classified 50% of the margins as being complete. Surgical oncologists should therefore understand the histologic margin status is influenced not only by the adequacy of excision but also by the method of margin assessment.