Published online Jul 27, 2023. doi: 10.4240/wjgs.v15.i7.1331
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
Processing time: 123 Days and 11.8 Hours
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.
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.
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.
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.
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.
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.
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.