Efficacy of manual dissection of lymph nodes in colon cancer resections

Abstract

The adequacy of lymph node dissection of colonic resection specimens influences the clinical and pathologic staging, leading to important postsurgical treatment decisions. Although manual lymph node dissection is the current standard at most institutions, recent statistical studies indicate that all lymph nodes, including those measuring 1-2 mm, should be recovered to be assured of lymph node negative status. Thus, we tested the efficacy of gross dissection by submitting the entire residual mesenteric fat. We analyzed 15 randomly chosen colonic resections (2 pT1, 1 pT2, 11 pT3, 1 pT4). After standard gross dissection of lymph nodes and submission of colonic material for diagnosis, the entire remaining mesenteric material was dehydrated over several days by serial washing in alcohol and acetone. All of the mesenteric tissue was submitted for histology. The average number of nodes found by original gross inspection was 20.8, while the average number of additional nodes found after clearing was 68.6. In all, 83% of the additional nodes were 2.0 mm or less in size. There were seven pN0 cases; one was upstaged by additional findings that may have been artifactual. There were four pN1 cases; three were upstaged to pN2 after submission of the mesenteric material. All four pN2 tumors had additional metastases identified. In all, 75% of all positive nodes were under 2.0 mm in size. In this limited sample, standard gross dissection proved sufficient for most pN0 tumors to remain node negative. However, our findings within the pN1 group show that examination of all of the mesenteric material may be necessary to be assured of correct pN status. Keywords: colon; adenocarcinoma; lymph node; clearing; dissection; staging; prognosisThe presence or absence of lymph node metastasis is pivotal for predicting the clinical outcome of patients who have undergone radical surgery for colorectal carcinoma.1 Lymph nodes are an integral component of the TNM classification system, a major determinant of adjunct therapy, and a prognostic marker in colorectal adenocarcinoma.2 Recovering a greater number of lymph nodes guards against missing a lymph node metastasis and allows for more accurate staging of patients. The identification of a single lymph node metastasis is sufficient to offer adjunctive therapy. The most important determinant of survival is the presence or absence of metastases in regional lymph nodes.3 Thus, the detection and examination of the largest possible number of lymph nodes are essential for correct staging, therapeutic decisions, and prognosis. 4,5 Despite claims of a meticulous search for lymph nodes in surgical specimens, wide variations in the number of total nodes and lymph node metastases continue to exist. 2,6,7 This variation may be due to the size of the specimen, the number of regional lymph nodes present in the specimen, and the number of nodes with metastases present.3,8 Pathologists also vary in their diligence, skill, and patience in dissecting the lymph nodes of a surgical specimen. 9In this study, we enr...

The clinical significance of lymph node size in colon cancer

“…Only 2 out of 305 affected lymph nodes were that small. Similar findings were reported by Brown et al 17 Several studies showed that the number of lymph nodes investigated is of remarkable prognostic relevance mainly in stage II but also in stage III colon cancer. There are three potential factors that could influence lymph node harvest and prognosis: the surgeon, the pathologist and the patient.…”

“…The metastatic involvement of lymph nodes as small as 1 mm is described in the literature. 17 However, the clinical significance of such findings is unclear. Radiologists screen their images for the occurrence of large lymph nodes (Z10 mm) in order to detect metastatic diseases.…”

Methylene blue injection into the rectal artery as a simple method to improve lymph node harvest in rectal cancer

“…This seems to be even more remarkable when taking into account that the average number of collected nodes in the unstained group is 1474, which is clearly above mean values reported in the literature for conventional techniques. 6,12,22 Fat clearance methods, or complete fat embedding, produced lymph node numbers between 55 and 87 10,17,23 and showed increased identification of positive nodes. However, these techniques are time consuming and laboring.…”

“…Therefore, a broad spectrum of techniques beginning with fat clearance methods to sentinel techniques has been introduced in order to increase lymph node counts and improve accuracy. [9][10][11] Nevertheless, dissection of lymph nodes in colorectal specimens is often time consuming and especially in cases of neoadjuvant radiotherapy frustrating. Increasing age, American Society of Anesthesiology grade, and preoperative radiotherapy are found to be factors for reduced lymph node harvest.…”

Meeting the 12 lymph node (LN) benchmark in colon cancer

“…There are advanced and resource demanding pathologic l techniques for fat clearance that would allow for the acquisition of even more lymph nodes than the standard techniques that are usually employed [32,33]. Furthermore, the numbers of lymph nodes can vary based on the location of the specimen resected as well as the body habitus and age of the patient [34][35][36].…”