Basic Study
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Surg. Jul 27, 2023; 15(7): 1331-1339
Published online Jul 27, 2023. doi: 10.4240/wjgs.v15.i7.1331
Histological study of the structural layers around the esophagus in the lower mediastinum
Toshifumi Saito, Satoru Muro, Hisashi Fujiwara, Yuya Umebayashi, Yuya Sato, Masanori Tokunaga, Keiichi Akita, Yusuke Kinugasa
Toshifumi Saito, Hisashi Fujiwara, Yuya Umebayashi, Yuya Sato, Masanori Tokunaga, Yusuke Kinugasa, Department of Gastrointestinal Surgery, Tokyo Medical and Dental University, Bunkyo-ku 113-8519, Tokyo, Japan
Satoru Muro, Keiichi Akita, Department of Clinical Anatomy, Tokyo Medical and Dental University, Bunkyo-ku 113-8519, Tokyo, Japan
Author contributions: Saito T, Muro S, Fujiwara H, Tokunaga M, Sato Y, Akita K and Kinugasa Y designed and coordinated the study; Saito T, Muro S, Umebayashi Y and Fujiwara H acquired and analyzed data; Saito T, Muro S, Sato Y, Fujiwara H, Tokunaga M, Akita K and Kinugasa Y interpret the data; Saito T and Fujiwara H wrote the manuscript; All authors approved the final version of the article.
Institutional review board statement: This study was reviewed and approved by the Institutional Review Board at Tokyo Medical and Dental University, No. M2018-210.
Informed consent statement: All study participants, or their legal guardians, provided informed written consent prior to study enrollment.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Hisashi Fujiwara, MD, PhD, Surgeon, Department of Gastrointestinal Surgery, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku 113-8519, Tokyo, Japan. fujsrg1@tmd.ac.jp
Received: March 20, 2023
Peer-review started: March 20, 2023
First decision: April 13, 2023
Revised: April 20, 2023
Accepted: May 22, 2023
Article in press: May 22, 2023
Published online: July 27, 2023
Abstract
BACKGROUND

In Japan, the transhiatal approach, including lower mediastinal lymph node dissection, is widely performed for Siewert type II esophagogastric junction adenocarcinoma. This procedure is generally performed in a magnified view using laparoscopy or a robotic system, therefore, the microanatomy of the lower mediastinum is important. However, mediastinal microanatomy is still unclear and classification of lower mediastinal lymph nodes is not currently based on fascia or other microanatomical structures.

AIM

To clarify the fascia and layer structures of the lower mediastinum and classify the lower mediastinal tissue.

METHODS

We dissected the esophagus and surrounding organs en-bloc from seven cadavers fixed in 10% formalin. Organs and tissues were then cut at the level of the lower thoracic esophagus, embedded in paraffin, and serially sectioned. Tissue sections were stained with Hematoxylin-Eosin (all cadavers) and immunostained for the lymphatic endothelial marker D2-40 (three cadavers). We observed the periesophageal fasciae and layers, and defined lymph node boundaries based on the fasciae. Lymphatic vessels around the esophagus were observed on immunostained tissue sections.

RESULTS

We identified two fasciae, A and B. We then classified lower mediastinal tissue into three areas, paraesophageal, paraaortic, and intermediate, using these fasciae as boundaries. Lymph nodes were found to be present and were counted in each area. The dorsal part of the intermediate area was thicker on the caudal side than on the cranial side in all cadavers. On the dorsal side, no blood vessels penetrated the fasciae in six of the seven cadavers, whereas the proper esophageal artery penetrated fascia B in one cadaver. D2-40 immunostaining showed lymphatic vessel connections between the paraesophageal and intermediate areas on the lateral and ventral sides of the esophagus, but no lymphatic connection between areas on the dorsal side of the esophagus.

CONCLUSION

Histological studies identified two fasciae surrounding the esophagus in the lower mediastinum and the layers separated by these fasciae were used to classify the lower mediastinal tissues.

Keywords: Esophagogastric junction, Histology, Mediastinum, Adenocarcinoma, Esophageal cancer, Gastric cancer

Core Tip: The transhiatal procedure including lower mediastinal lymph node (LN) dissection is widely performed to treat esophagogastric junction (EGJ) adenocarcinoma. However, microanatomy of the lower mediastinum is unclear and the classification of lower mediastinal LNs is obscure. Therefore, we performed a histological study to investigate the microanatomy of the lower mediastinum in seven cadavers. We identified two fasciae surrounding the esophagus in the lower mediastinum and classified the periesophageal lower mediastinal tissue into three areas based on these fasciae. LNs were found within all classified areas. These data provide useful landmarks for EGJ adenocarcinoma surgery.