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    • The major point for colorectal cancer surgery is to include

    2018-11-12

    The major point for colorectal cancer surgery is to include resection of the regional order Bindarit node and mesenterium in addition to the colorectum. For patients with rectal cancer, the adequacy of the distal margin is dependent on both the risk for intramural tumor spread and the distal mesorectal lymphatic spread. Tumor cell deposits within the mesorectal lymph nodes have been identified up to 5 cm distal to the inferior aspect of the tumor, emphasizing the need to adhere to the principles of total mesorectal excision and giving rise to the concept of tumor-specific mesorectal excision (mesorectal transection 5 cm distal to the inferior border of the tumor) for more proximal rectal cancers. A systematic review of studies by Bujko et al identified 17 studies showing results in relation to margins of approximately <1 cm (948 patients) versus >1 cm (4626 patients); five studies in relation to a margin ≤5 mm (173 patients) versus >5 mm (1277 patients), and five studies showing results in a margin ≤2 mm (73 patients). The local recurrence rate was 1.0% higher in the <1-cm margin group compared with the >1-cm margin group (p = 0.175). In the selected group of patients, <1-cm margin did not jeopardize oncologic safety after sphincter-preserving surgery for rectal cancer, which was also the same conclusion in another report. It was suggested that the safety margin may be reduced to 1 cm or even 0.5 cm by preoperative radiotherapy. Therefore, preoperative radiotherapy may extend the indications for a sphincter-saving operation. However, a report by Kwak et al suggested that a distal margin of at least 5 mm with a negative resection margin on frozen section examination does not reduce oncological safety in patients with rectal cancer who receive preoperative or postoperative chemoradiotherapy. The length will be shorter if the patient undergoes additional treatment along with preoperative radiation. However, there is no excuse for the extension of the resection of mesocolon no matter how short the resection margin is from the tumor.
    Discussion In general, wide excision of a malignant tumor with an adequate margin is important to ensure disease eradication and recurrence. The existing evidence is based on pathological findings to determine a positive or negative safety margin or involvement of a tumor capsule. However, one thin slice of pathological tissue cannot represent the entire resection margin tissue, meaning the positive or negative result obtained may or may not be correct. Therefore, it is difficult to truly ascertain the condition, because the actual status cannot be obtained by pathological findings on a thin slide, especially when using a false-negative resection margin. In this situation, false-negative results will be high, because the entire tissue around the tumor resection margin is not examined. In addition, skip metastatic lesion or bloodstream metastatic cancer is commonly found while performing an oncological surgery in our patients as shown in the Fig. 1. Such a concept may also be applicable to HCC, which is characterized by unique pathologic features. Intrahepatic spread mainly occurs by portal venous invasion, which is completely different from the invasion of tumors into the surrounding tissues. Multicentric recurrence is common in HCC and could occur anywhere in the liver remnant. The relation between the resection margin and the pattern of recurrence shows that in both the narrow and wide margin groups, most recurrences occurred in the liver remnant at a distal segment or multiple segments, indicating an origin from either intrahepatic metastasis or multicentric carcinogenesis. The margin width did not have prognostic significance in relation to the underlying liver cirrhotic status or the extent of resection. This has an important implication for avoiding extensive resection of HCC associated with cirrhosis. Without question, a positive histological margin is associated with a higher incidence of postoperative recurrence, but a postoperative recurrence could be related to the underlying venous invasion or microsatellites rather than the resection margin. Most intrahepatic recurrences were considered to arise from intrahepatic metastasis by venous dissemination, which a wide resection margin could not prevent. Although surgeons would prefer to have a wide margin to achieve a better prognosis, various factors exist based on the path of carcinogenesis.