| Part One: Application of lymph node revealing solution in the detection of lymph nodes in rectal cancerObjective Severe drawbacks exist in the conventional pathological examination with manual palpation, which might miss small or minute lymph nodes in the mesentery. This part of study was devoted to investigate the feasibility and efficiency of lymph node revealing solution (LNRS) in the harvest of mesorectal lymph nodes in rectal cancer.Methods Thirty-one rectal cancers operated with total mesorectal excision from October 2001 to October 2002 were prospectively collected. Rectal specimens resected were processed with lymph node revealing solution to harvest lymph nodes, which were examined with hematoxylin & eosin (HE) staining.Results After immerse of the specimens in the solution for 6 hours or more, lymph nodes were identified as white, chalky nodules against the yellow background of adipose. A total of 548 nodes were harvested from the 31 rectal specimens, with 17.7±8.2 nodes per case. 114 nodes from 22 patients were detected positive by HE staining, with 5.2±5.1 positive nodes per case. The mean size of all nodes was 4.1±1.8 mm in diameter. The mean size of metastatic nodes was 5.2±1.7 mm in diameter, with negative nodes 3.8±1.7 mm (P=0.000). Among the 548 nodes, 92 nodes (16.8%) were ≤2 mm, with 4 nodes positive (4.3%); 182 nodes (33.2%) were ≥5 mm, with 54 nodes (47.4%) positive; and 274 nodes (50.0%) were between 2 and 5 mm, with 56 nodes (49.1%) positive.Conclusion The majority of lymph nodes and tumor positive lymph nodes within the mesorectum are smaller than 5 mm in diameter. Lymph node revealing technique is a simple and feasible method in collecting lymph nodes, which helps to effectively identify small and minute lymph nodes in the mesorectum that are easily missed by conventional method. Part Two: Distribution and patterns of lymph nodes metastases and micrometastases in the mesorectum of rectal cancerObjective Lymph nodes contained in the mesorectum are the earliest and most frequent ones that might be involved when tumor spread takes place. Focused examination of the mesorectal lymph nodes could identify most of the tumor metastatic and micrometastatic foci. Up to now, few studies on the distribution of mesorectal lymph nodes are available, and the patterns of lymph nodes metastases and micrometastases remain to be fully understood. This part of study was devoted to investigate the distribution and patterns of lymph nodes metastases and micrometastases in the mesorectum, with an aim to provide anatomicopathological evidences for the choice of optimal procedure in the surgical management of rectal cancer. Methods Thirty-one rectal cancer specimens collected were subjected to the processing of lymph node revealing solution. Lymph nodes harvested were recorded by the anatomical locations, which then were examined with a combination use of hematoxylin & eosin (HE) and immunohistochemical (IHC) staining to detect tumor metastases and micrometastases. Results A total of 548 nodes in 31 specimens were harvested, among which 114 nodes (mean size, 5.2±1.7 mm) from 22 specimens (71.0%) were detected to have tumor metastases, with 5.2 nodes per case, and 39 nodes (mean size, 3.9±1.4 mm) from 18 specimens (58.1%) have tumor micrometastases, with 2.2 nodes per case. Of these tumor micrometastatic patients, 5 cases were previously diagnosed negative by HE examination, thus these group of patients were upgraded.Among the 27 nodal positive cases, 5 case were with tumor above the peritoneal reflection, and a total of 81 nodes were harvested, with 18 nodesmetastatic and 4 nodes micrometastatic, most of which were located along the branches and the trunk of the superior rectal artery (SRA); 22 cases were with tumor at or below the peritoneal reflection, and 418 nodes were collected, with 96 nodes metastatic and 35 nodes micrometastatic, which were distributed at the peritumoral space (10%), along the middle rectal artery (MRA) (6.1%) and the branches and the trunk of SRA (84%), respectively.Classified by the circumferential location of main lump at the rectal wall, 15 ones were posterior wall located tumor with 78 nodes metastatic and micrometastatic, of which 25 (27.8%) and 30 (31.7%) positive nodes were scattered along both branches of the SRA (iMJ.627). 12 ones were lateral located tumor with a total of 75 nodes metastatic and micrometastatic. The incidences of nodes spread along the branches of SRA on tumor side and opposite side were 43.0% (37 nodes) and 16.1% (9 nodes) (P=0.001), the rates of nodes spread along the middle rectal artery (MRA) on tumor side and opposite side were 40.0% (8 nodes) and none respectively (P=0.014). Conclusion The patterns of lymph node metastases and micrometastases within the mesorectum were consistent with the distribution of most mesorectal lymph nodes. The spread of lymph nodes metastases and micrometastases was affected by the segment of tumor location in the rectum: tumor above the peritoneal reflection spreads mainly along the SRA, and tumor at and/or below it might spread upward along the SRA and laterally along the MRA. On the other hand, the spread of lymph nodes metastases and micrometastases was also closely related to the circumferential situation of tumor in the rectal wall: posterior wall located tumor might spread along both sides of the mesorectum simultaneously, while lateral wall located tumor tended to spread preferably along the mesorectum on tumor side. These observations emphasize the importance of complete excision of the tumorside mesorectum, and in carefully selected cases with lateral wall restricted tumor, the procedures of selective unilateral total mesorectum excision (ULTME) or selective unilateral lymphadenectomy might be sufficient. Part Three: Distribution of sentinel lymph nodes in rectal cancer and drainage of lymphatic flowObjective The spread of lymph node follows an orderly anatomical way in most solid tumors. Sentinel lymph nodes (SLN) are the first (one or) few lymph nodes that receive the lymphatic drainage of tumor area, and are also be the first nodes that might be involved when lymph node spread occurs. Researches of in vivo SLN mapping on colorectal cancers demonstrated that the status of sentinel lymph nodes (SLN) can accurately predict the tumor status of regional nodal basin. Focused examination of the SLN could identify most tumor metastatic and micrometastatic diseases. This part of study was aimed to evaluate the feasibility of ex vitro SLN mapping in rectal cancer, and meanwhile to explore the patterns of lymph nodes spread by investigating the anatomical distribution of SLN and dynamic observation of the lymphatic flow.Methods Thirty-four patients with rectal cancer operated between May 2004 and July 2004 in West China Hospital were prospectively included. Ex vitro SLN mapping were performed on all specimens within 30 minutes after resection. The blue stained SLN in the mesorectum were harvested, with the direction of lymph flow recorded.Results Of the 34 cases included, ex vitro SLN mapping were successfully performed on 33 cases (97.1%). A total of 56 SLN were identified, with 1.6 ± 0.8 nodes per case. The average distance from SLN to tumor was 2.0 ± 1.5 cm. 39 nodes (9/56, 69.6%) and 20 metastatic nodes (20/24, 83.3%) were within the distance of 2.0 cm. Among the 15 cases with non-SLN positive examined by HE, 12 of them (80%) were also with one or more SLN positive. Of the 19 cases with non-SLN free of tumor metastases, 7 cases (36.8%) hadSLN metastases. The sensitivity of SLN in the prediction of regional nodal basin was 86.4% (19/22), and the false negative rate was 9.1% (3/33). Among the 33 successful cases, 4 cases were with tumor above the peritoneal reflection, in which 2 cases (50%) were with SLN in the tumor plane and 2 cases (50%) above it. The observed lymphatic flows in these cases run upward along the superior rectal artery (SRA). In the other 29 cases with tumor at or/and below the peritoneal reflection, 25 cases (86.2%) were with SLN above the tumor plane, with 3 cases (10.3%) in the plane and 1 case (3.4%) below the plane. The directions of lymphatic flow were coincident with the anatomical distribution of SLN, which mainly run upward along the SRA, and in a few cases lateral spread along the middle rectal artery was observed, and inverse downward spread occurred in one case. Classified by the circumferential location of main lump at the rectal wall, 7 ones were anterior wall located tumor, in whom 5 cases were with SLN at the peritumoral space, with one case in the posterior mesorectum and one case in the lateral mesorectum. Lateral and posterior upward running of the lymphatic flows were observed in these cases. Of the 10 cases with lateral wall located tumor, 2 cases were with SLN at the peritumoral space, and 5 cases with SLN along the branche of the SRA on tumor side, and another 3 cases along the tumor side middle rectal artery (MRA). Lymphatic flows in them run mainly upward and/or laterally along the mesorectum at tumor side. In the other 16 cases with posterior located tumor, 4 cases were with SLN at the peritumoral space, and 6 cases in the posterior mesorectum, and another 2 and 4 cases in the bilateral mesorectum, respectively. Lymphatic flows in theses cases runs posterior upward and/or outside laterally. Conclusion The application of ex vitro SLN mapping in rectal cancer is feasible and efficient, with a sensitivity of 86.4% and an acceptable false negative rate (9.1%). The observed lymphatic flow was in accordance withthe distribution of SLN, which was not only affected by the segment of tumor location in the rectum, but also closely related to the circumferential situation of tumor in the rectal wall: lymphatic flow of the anterior wall located tumor runs posterior upward or laterally outside, in lateral wall located tumor it runs preferably posterior upward along the SRA on tumor side and/or laterally along the MRA on tumor side, while in posterior wall located tumor it could run posterior upward and/or outside bilaterally.
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