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
ARTICLE HIGHLIGHTS
Research background

Cases of the esophagogastric junction (EGJ) adenocarcinoma are increasing in number worldwide; however, there is no consensus on the surgical treatment for EGJ adenocarcinoma, especially Siewert II cases. In Japan, the transhiatal approach is widely performed for Siewert type II cases, and the right thoracic approach is widely performed for Siewert type I cases.

Research motivation

Because procedures for EJG adenocarcinoma are often performed with a magnified view, the microanatomy of the lower mediastinum is extremely important for surgeons. However, there is no consensus regarding the fascial and layer structures of the lower mediastinum. Furthermore, the boundaries of the mediastinal lymph nodes are unclear.

Research objectives

We examined the microanatomy, especially the fascial and layer structures, of the lower mediastinum and the boundaries of periesophageal tissue in the lower mediastinum in the present histological study of seven cadavers.

Research methods

The esophagus and surrounding organs were resected at the level of the lower thoracic esophagus and embedded in paraffin, and serial 5-μm sections were made. We performed hematoxylin-eosin staining on all cadavers and D2-40 staining on three cadavers.

Research results

We identified two fasciae around the esophagus, and we classified the lower mediastinal tissue into three areas based on these two fasciae. The tissue on the dorsal side of the esophagus was thicker on the caudal side than on the cranial side. D2-40 staining revealed lymphatic connections between the paraesophageal tissue and the external area in the lateral and ventral regions of the esophagus; however, there were no lymphatic connections between areas in the dorsal region of the esophagus.

Research conclusions

This histological study revealed two fasciae surrounding the lower thoracic esophagus and the layer structures separated by these fasciae. These findings will help to establish a new classification system for the lower mediastinal tissues.

Research perspectives

These results can provide useful landmarks for treatment procedures in patients with EJG adenocarcinoma. Our research findings will also support further clinical studies, such as those focusing on the therapeutic value of mediastinal lymph node dissection.