AdenoCA of Colon : Lymph Node Metastases
Lymph Node Metastases in Colorectal Cancer: Regional lymph nodes are located along the course of the major vessels supplying the colon and rectum, along the vascular arcades of the marginal artery, and adjacent to the colon (mesocolic borders). The number of lymph nodes sampled is recorded in the report. The greater the number of nodes removed and evaluated, the greater the accuracy in staging which correlates with improved survival. At least 12 lymph nodes should be examined in colon and rectum resections performed for cure. In cases where surgery is performed for palliation or in patients who receive preoperative radiation and/or chemotherapy, fewer lymph nodes may be found. pNx: Regional lymph nodes cannot be assessed. pN0: All nodes are histologically negative, even if fewer than recommended number. pN1: Involvement of 1 to 3 lymph nodes by metastasis. pN1a = 1 positive lymph node. pN1b = 2 to 3 positive nodes. pN1c: No regional lymph nodes are positive but there are tumor deposits in the subserosa, mesentery, or nonperitonealized pericolic or perirectal/mesorectal tissues. pN2: Metastatic deposits in 4 or more regional lymph nodes. pN2a = 4 to 6 positive lymph nodes. pN2b = 7 or more positive lymph nodes. Within N1 and N2 groups, the subgroups with fewer positive lymph nodes have a better prognosis. Positive lymph nodes that are outside the regional drainage area of the primary tumor are considered distant metastases. Isolated Tumor Cells: Defined as single cells or small clusters of tumor cells in a lymph node measuring less than or equal to 0.2 mm. Nodes with isolated tumor cells are considered N0. Micrometastases: Tumor deposits measuring > 0.2 mm but less than or equal to 2 mm in a lymph node. Such nodes are considered N1(mic). This image shows a small lymph node embedded in the serosal fat and containing metastatic signet ring cell carcinoma of colon. Clusters of signet ring cells within pools of mucin can also be seen.