Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 30

There are several considerations that make the comparison of evidence in the literature and subsequent adjustment of surgical planning difficult. There are distinct and widely different concepts of what constitutes the definition of a “margin” and how the quality or magnitude of margins are reported. Margins may refer to: (i) the intraoperative margin (i.e. the normal tissue margin as measured in situ between palpable tumor and the planned incision), (ii) the width of normal tissue beyond palpable tumor and the resected edges as measured after resection and before fixation, (iii) the measured width of tissue beyond the palpable tumor after fixation, and (iv) the measured width of normal tissue between the nearest microscopic tumor cell and the resected edge as seen by a pathologist on the slide. Each of the above margin assessment methods represents very different measurements, yet it is rare for veterinary journal articles to report which of these margin assessment methods is being used or even the magnitude of the resected margin beyond a description of “wide,” “marginal,” or “incomplete.” A recent study (Terry et al. 2017) showed that there was significant difference in the measured grossly normal surgical margins following sarcoma removal after resection compared to the planned intraoperative excision margin. Therefore, surgeon intent (wide or marginal) should not be considered an acceptable means of reporting margins obtained. In addition, these same authors noted that comparison of subgross evaluation of tumor‐free margins, once sectioned and placed on a slide, was not at all comparable to the magnitude of the pathologist‐reported histological tumor‐free margin.

In human medicine, there has been a shift in margin assessment schemes from a traditional Enneking‐style margin assessment (intralesional, marginal, wide, or radical) to either a distance method (reporting the minimum distance between the nearest observed tumor cell and the inked surgical margin) or a qualitative method, where resected specimens are classified as R0 (no tumor at the inked edge), R1 (microscopic tumor at the inked edge), and R2 (residual gross disease left in patient). This highlights the important difference between surgical margins in situ versus histologic margins. Recent reports comparing the distance method to the qualitative method indicate that with osteosarcoma the distance method in combination with tumor response to chemotherapy (>90% or <90%) was the best predictor of local recurrence (Cates 2017). Conversely, in soft tissue sarcomas of the extremity, the qualitative assessment was most predictive and the distance method was not (Harati et al. 2017). It is likely, therefore, that different methods of margin assessment will have differing prognostic significance in veterinary surgical oncology.