Elsevier

Human Pathology

Volume 38, Issue 5, May 2007, Pages 762-767
Human Pathology

Original contribution
Additional lymph node examination from entire submission of residual mesenteric tissue in colorectal cancer specimens may not add clinical and pathologic relevance

https://doi.org/10.1016/j.humpath.2006.11.005Get rights and content

Summary

The examination of lymph nodes in colorectal cancer is a critical procedure for determining the stage, which determines prognosis and need for adjuvant therapy. The current recommendation is to harvest at least 12 lymph nodes by conventional manual node dissection (MND). Recent studies have suggested that all lymph nodes in mesenteric tissue should be retrieved using a special method such as the entire submission of residual mesenteric tissue (ESMT) after MND. We investigated the efficacy of ESMT with its potential impact on the pN stage. After an MND in 48 consecutive colorectal cancer resection specimens, the residual mesenteric tissues were entirely submitted for routine histologic examination by ESMT. After initial MND, 933 (mean, 19.4) lymph nodes were found, and there were 29 pN0, 10 pN1, and 9 pN2 cases. By ESMT after MND, 1132 (mean, 23.6) additional lymph nodes were found. Most (88.6%) of them were 2.0 mm or less in maximum dimension, and of the 1132 additional lymph nodes, 14 (1.2%) lymph nodes revealed tumor metastases. Although there was no additional nodal metastasis in any of the initial 29 pN0 cases, additional nodal metastases were found in 10 of the original 19 node-positive cases. Two of the 10 cases with additional positive nodes identified would be upstaged from pN1 to pN2. Both of these cases had fewer than 12 nodes identified by MND but had 1 and 2 additional nodes identified by ESMT. Our study demonstrated that MND seems to be accurate and efficient in evaluating tumors with pN stage of pN0. Although ESMT may be useful to assess the correct pN stage in pN1 cases with fewer than 12 lymph nodes in MND, it may not add any additional information in pN0 cases or in node-positive cases with 12 or more lymph nodes found by MND.

Introduction

The status of lymph node metastasis (the pN qualifier) in colorectal cancer is an integral component of pathologic tumor staging, which in turn determines the prognosis and the need for adjuvant therapy [1], [2], [3], [4]. The pN stage has been subclassified into the pN0, pN1, and pN2 categories, according to the presence or absence of lymph node metastasis and the number of metastatic lymph nodes; the pN0 stage refers to the absence of positive lymph nodes, whereas pN1 refers to the presence of 1 to 3 lymph nodes positive for metastatic tumor and pN2 designates 4 or more positive lymph nodes [1]. Studies have shown that the lymph node status, as described hereinabove, is an independent prognostic factor [1]. The minimum number of harvested lymph nodes needed to correctly assess the pN status in colorectal cancer is a controversial topic [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. The College of American Pathologists recently published a consensus statement recommending that examination of at least 12 lymph nodes is necessary for accurate staging [6], [14], [15].

The fat clearance technique was first used in 1938, and since then, other similar methods have been developed to isolate lymph nodes in colon resection specimens [16], [17], [18], [19]. Although this technique may be optimal to improve the yield of lymph nodes, it is time consuming, labor intensive, and cost ineffective, and it delays reporting. There has been significant variation and inconsistency among the different methods regarding harvesting and processing of lymph nodes [14]. Recently, Brown et al [16] reported that complete submission of the mesentery, a variation of the fat clearance technique, may be necessary to assess the correct pN status within the pN1 group.

We investigated the efficacy of additional lymph node dissection by entire submission of residual mesenteric tissue (ESMT) with its potential impact on the pN status and also the characteristics of lymph nodes found by ESMT.

Section snippets

Case selection

Forty-eight patients with colorectal cancer who underwent surgical procedures were consecutively selected and prospectively investigated from 3 different institutions (Ulsan University Hospital, Ulsan, Korea; Asan Medical Center, Seoul, Korea; and National Cancer Center, Ilsan, Korea) between April and October of 2004. Resection specimens without mesenteric tissue were not included in our study. Cases with other tumor types such as gastrointestinal stromal tumor, carcinoid tumor, lymphoma, or

Clinicopathologic features

The mean patient age was 60.5 years (range, 41-79 years; median, 61 years), and the male-to-female ratio was 1.7 (30 males, 18 females). Of the 48 cases, there were 6 T1, 7 T2, 29 T3, and 6 T4 cases. Designation of pN status resulted in 29 pN0, 10 pN1, and 9 pN2 cases. With respect to tumor location, there was 1 descending, 11 sigmoid, 2 rectosigmoid, and 34 rectal carcinoma cases. No cases of right colon or transverse colon cancer were included in this study. The mean resection specimen length

Discussion

Retrieval of an adequate number of lymph nodes is essential for correct tumor staging, choice of the therapy, and determination of prognosis. However, there is frequently wide variation in the total number of harvested lymph nodes and the number of metastatic lymph nodes identified in individual cases [2], [11], [12]. Possible reasons include variations in the patients' immune system, anatomic location, surgical technique, tumor T or N stage, method of lymph node retrieval, and examining

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