The Prognostic Significance of Number of Lymph Node Metastasis in Colon Cancer – Based on Japanese Techniques of Resection and Handling of Resected Specimens

Staging systems for cancer reflects the prognosis of the disease and it is used to choose the modality of treatment. The TNM classification has mainly been used in the west. In Japan, Japanese classification according to General Rules for Clinical and Pathological Studies on Cancer of the Colon, Rectum and Anus(JGR)(Japanese Society for cancer of colon and rectum, 2009) is used. The degree of the lymph node metastasis in each staging system has some variations. In 2009, 7th edition of (JGR, 2009) was revised to make it uniform with the 6th edition of TNM classification (Sobin & Wittekond, 2002). However, the 7th edition of TNM classification (Sobin et al., 2009) was further revised where the category of nodal status was subdivided (Table 1) on the basis of number of positive lymph nodes. The validity of which is based on the pooled SEER database of 109,953 cases of colorectal cancer lymph node metastases (Gunderson et al., 2010). Japanese classification of nodal status takes into account not only the number of positive lymph nodes but also the site from where they are retrieved according to the location of the tumor. Our study showed recategorization of lymph nodes such as 1, 2 to 6 and 7 or more lymph nodes with metastasis reflected the prognosis of the disease (Akagi et al., 2010). Thus, the number of lymph nodes retrieved plays a vital role in the staging system and is one of the main prognostic indicators of the disease. The various techniques of resection and handling of resected specimens may also vary according to different institutions and countries. The number of lymph nodes retrieved can depend on different factors like the surgical technique, length of resection, mesocolic excision, lymph node dissection, handling of resected specimen and criteria for pathological diagnosis which has some differences in Japan as compared to the west. Moreover, chemotherapy protocols and treatment of recurrence also may vary in different places. This can alter the stage, recurrence rate, as well as the outcome of the disease. Therefore, here we have elaborated our technique of resection, specimen handling and nodal dissection which is uniformly practiced in all centers of Japan and present data from our center where these techniques have been carried out consecutively.