Histological study of the thin membranous dense connective tissues around the curving portion of the bilateral recurrent laryngeal nerves.

OBJECTIVE/AIM: We aimed to demonstrate the anatomical relationship between the recurrent laryngeal nerves (RLNs), thin membranous dense connective tissue (TMDCT [e.g., the visceral or vascular sheaths around the esophagus]), and the lymph nodes around the esophagus at the curving portion of the RLNs for rational and efficient lymph node dissection. METHODS: Transverse sections of the mediastinum at 5 mm or 1 mm intervals were obtained from four cadavers. Hematoxylin and eosin staining and Elastica van Gieson staining were performed. RESULTS: The visceral sheaths could not be clearly observed the curving portions of the bilateral RLNs, which were observed on the cranial and medial side of the great vessels (aortic arch and right subclavian artery [SCA]). The vascular sheaths could be clearly observed. The bilateral RLNs diverged from the bilateral vagus nerves, which ran along with the vascular sheaths, went up around the caudal side of the great vessels and the vascular sheath, and ran cranially on the medial side of the visceral sheath. Visceral sheaths were not observed around the region containing the left tracheobronchial lymph nodes (No. 106tbL) or the right recurrent nerve lymph nodes (No. 106recR). The regions containing the left recurrent nerve lymph nodes (No. 106recL) and the right cervical paraesophageal lymph nodes (No. 101R) were observed on the medial side of the visceral sheath, with the RLN. CONCLUSION: The recurrent nerve, which branched off from the vagus nerve descending along the vascular sheath, ascended the medial side of the visceral sheath after inversion. However, no clear visceral sheath could be identified in the inverted area. Therefore, during radical esophagectomy, the visceral sheath along No. 101R or 106recL may be recognized and available.

[A Case of HER2 Positive Unresectable Gastric Cancer Leading to Conversion Therapy with Chemotherapy].

A 72‒year‒old man visited our hospital with a chief complaint of epigastralgia. Upper gastrointestinal endoscopy revealed type 3 advanced gastric cancer at the body of the stomach. Following an investigation, he was diagnosed with human epidermal growth factor receptor 2‒positive gastric cancer with invasion to the pancreas as well as the paraaortic lymph node, and multiple liver metastases were also observed. The cancer was judged to be cT4a, N2M1(H1 LYM: No. 16), cStage Ⅳ and thus was considered suitable for chemotherapy. We performed capecitabine plus cisplatin plus trastuzumab therapy. After 3 courses, the primary lesion and swollen lymph nodes decreased in size. After 20 chemotherapy courses, the primary lesion relapsed, so conversion surgery was performed. The patient underwent total gastrectomy, distal pancreatectomy, and partial resection of the liver. We planned to perform adjuvant chemotherapy, but the patient declined it because of anorexia. At 18 months after the operation, recurrence of the tumor was detected at the celiac artery. Chemotherapy was performed as follows: capecitabine plus trastuzumab 10 courses, ramucirumab plus paclitaxel, irinotecan, and nivolumab. However, the patient eventually died 71 months after the first visit.

The evaluation of the gastric tube blood flow by indocyanine green fluorescence angiography during esophagectomy: a multicenter prospective study.

OBJECTIVE: We determined the anastomotic site during gastric tube reconstruction in esophagectomy according to the "90-to 60-s rule" using indocyanine green (ICG) fluorescence angiography. We evaluated its safety and efficacy in a prospective multicenter setting. METHODS: We enrolled 129 patients who underwent subtotal esophagectomy for esophageal cancer. ICG fluorescence angiography was performed after making a wide gastric tube, and the time from the initial enhancement of the right gastroepiploic artery to the tip of the gastric tube was used as a parameter. Esophago-gastro anastomosis was made at the area that was enhanced within 90 s (preferably within 60 s). The enhancement time and the incidence of anastomotic leakage were compared. RESULTS: In all cases, anastomosis was made at the site enhanced within 90 s. Anastomotic leakage was found in only 4 (3.1%) of 129 cases; specifically, it was detected in 3 (2.4%) of 126 cases whose anastomotic site was enhanced within 60 s and in 1 (33.3%) of 3 cases where the enhancement time exceeded 60 s (p = 0.09). CONCLUSIONS: Determining the anastomotic site using the 90-to 60-s rule with ICG imaging in gastric tube reconstruction helps reduce the rate of anastomotic leakage.

Histological study of the thin membranous dense connective tissue around the middle and lower thoracic esophagus, caudal to the bifurcation of the trachea.

OBJECTIVE: We previously reported on the thin membranous dense connective tissue around the esophagus in the upper mediastinum. This time, we histologically investigated the existence of similar structures in the middle and lower mediastinum, caudal to the bifurcation of the trachea. METHODS: Semi-sequential transverse sections of the mediastinum were obtained from two cadavers. Hematoxylin and eosin staining and Elastica van Gieson staining were performed. RESULTS: In the middle mediastinum, the "visceral sheath" could not be observed completely around the esophagus. In the lower mediastinum, the thin membranous dense connective tissue was observed beneath the pericardium on the ventral side of the esophagus. On the dorsal side of the esophagus, two thin membranous dense connective tissues were similarly observed in two cadavers. One existed between the dorsal side of the esophagus and the three vessels (i.e., the descending aorta, the azygos vein and the thoracic duct) and was integrated with the thin membranous dense connective tissue of the ventral side of the esophagus at the bilateral side of the esophagus. This integrated dense connective tissue reached the left subpleural region and the adventitia of the aorta on the left side and the peripleural and pulmonary hilum on the right side. The other thin membranous dense connective tissue, which represents the "vascular sheath", was observed between the descending aorta and the thoracic duct. CONCLUSION: These two thin membranous dense connective tissues, which are considered to represent the visceral sheath and vascular sheath, are thought to be available as optimal dissecting layers for radical esophagectomy.

Histological changes in the human esophagus following triamcinolone injection to prevent esophageal stricture after endoscopic submucosal dissection.

BACKGROUND: Locoregional steroid injection prevents post-endoscopic submucosal dissection (ESD) esophageal stricture, but histological changes that occur following steroid injection in the human esophagus are unclear. This study investigated the histopathological characteristics caused by locoregional triamcinolone acetonide (TA) injection using human esophagectomy specimens. METHODS: From January 2014 to December 2019, among 297 patients (373 lesions) who underwent esophageal ESD, 13 patients who underwent additional esophagectomy after ESD were examined. Seven patients (TA group) with wide excisions were injected with TA after ESD and another six patients (Non-TA group) with smaller tumors were not injected with TA. The clinical background of these patients and histopathological features of ESD ulcer scar obtained from esophagectomy specimens were retrospectively investigated. RESULTS: The circumferential rate of ESD excision was more than three-quarters in all cases in the TA group, whereas it was less than three-quarters in the Non-TA group. No other statistical difference in the clinical background was found between the two groups. The subepithelial fibrous tissue of the ESD ulcer scar in the TA group was significantly thinner than that in the Non-TA group (P < 0.05). There was no significant difference in the thickness of the regenerated epithelium and muscularis propria layer of the ESD ulcer scar. CONCLUSIONS: Histological finding of thinning of the subepithelial fibrous tissue of ESD ulcer scar in the human esophagus after TA injection was obtained. This suggests that TA suppresses the proliferation of the fibrous tissue of the subepithelial layer to help prevent esophageal stricture after widespread ESD in the human esophagus.

[REPARATIVE SURGERY OF PRESSURE-REGULATING BALLOON HERNIA AFTER ARTIFICIAL URINARY SPHINCTER REPLACEMENT: A CASE REPORT].

A 74-year-old male with post-prostatectomy incontinence underwent artificial urinary sphincter replacement due to device malfunction. Three months after the replacement surgery, he presented for a consultation due to a bulging area in his lower abdomen. Computed tomography revealed a hernia of the pressure-regulating balloon (PRB), while the device was working well. In the reparative surgery, reopening the lower abdominal incision, the PRB was carefully restored to its previous position after creating a sufficient submuscular space. As the rectus abdominis fascia showed an adequate strength, the fascia was tightly sutured without using a prosthetic mesh. Thereafter, the patient has been free from incontinence for two and a half years without hernia recurrence. Given the mechanical nature of the device, replacement surgery is sometimes required over time. Tissue fragility due to repetitive surgeries and increasing ambient pressure due to space reduction derived from the PRB deflation could cause PRB hernia. Such cases can be treated under careful manipulation without damaging the device. Considering the future potential need for repeated surgery, it would be preferable not to use prosthetic mesh, as it can cause dense adhesion.

The Impact of Hybrid Minimally Invasive Esophagectomy with Neck-Abdominal First Approach on the Short- and Long-Term Outcomes for Esophageal Squamous Cell Carcinoma.

BACKGROUND: Currently, there is no consensus for an optimal minimally invasive esophagectomy (MIE) approach. This study aimed to compare hybrid MIE (hMIE) with neck-abdominal first approach to standard open esophagectomy (OE). METHODS: Data from a cohort of 301 patients were retrospectively analyzed. All participants received either hMIE or OE for the treatment of esophageal squamous cell carcinoma at Tokyo Medical and Dental University between January 2003 and December 2013. Analyses included propensity score matching and the Kaplan-Meier statistical method to determine overall survival (OS) and disease-free survival (DFS) of the cohort. RESULTS: After one-to-one propensity score matching, there were 68 patient pairs. The hMIE group had significantly lower incidence of severe postoperative complications (20.1% vs. 7.4%; p = 0.026) and severe respiratory complications (7.4% vs. 0%; p = 0.058) than the OE group. The 5-year oncological outcomes of the two groups were almost equivalent (OS: OE, 55.0%; hMIE, 69.0%; p = 0.063 and DFS: OE, 54.0%; hMIE, 62.0%; p = 0.28). CONCLUSIONS: This study compared hMIE with neck-abdominal first approach to standard OE. The results showed significantly less severe postoperative complications for hMIE with neck-abdominal first approach in comparison with OE, without a compromise in long-term oncological outcomes.

The evaluation of the hemodynamics of a gastric tube in esophagectomy using a new noninvasive blood flow evaluation device utilizing near-infrared spectroscopy.

OBJECTIVE: We herein evaluated the hemodynamics of a gastric tube in esophagectomy using a new noninvasive blood flow evaluation device utilizing near-infrared spectroscopy. METHODS: Thirty-two cases of subtotal esophagectomy and gastric tube reconstruction for esophageal cancer were studied. The new device measures the regional tissue saturation of oxygen (rSO2: 0-99%) and total hemoglobin index (T-HbI: 0-1.0) with a small sensor. We measured these values at the antrum (point A), final branch of the right gastroepiploic artery (point B) and planned anastomotic point (point C) before and after gastric tube formation. The values at the three points were compared, and the gradients at the three points from before to after gastric tube formation were compared. RESULTS: The mean values of rSO2 at point A, B, and C before gastric tube formation were 57.2%, 57.8% and 56.0%, and those after formation were 54.6%, 58.0% and 55.8%, respectively. There was no significant difference in the comparison of the rSO2 gradient before and after formation (p = 0.167). The mean values of T-HbI at point A, B, and C before formation were 0.126, 0.178 and 0.211, and those after formation were 0.167, 0.247 and 0.292, respectively. There was no significant difference in the gradient of the increase before and after formation (p = 0.461). CONCLUSION: A new device has shown that the gastric tube used in our facility is one that maintains tissue saturation of oxygen and does not cause excessive congestion at anastomosis.

Flexible Gastric Tube: A Novel Gastric Tube Formation Method to Prevent Anastomotic Leakage.

Gastric tube reconstruction is now the method most frequently used for digestive tract reconstruction after the resection of esophageal carcinoma. In our institute, a "flexible" gastric tube designed to supply a sufficient amount of blood to the tip of the gastric tube (the same as a subtotal gastric tube) and simultaneously provide sufficient length for tension-free anastomosis in the cervical surgical field (the same as a narrow gastric tube) was introduced. This gastric tube formation method has contributed to reducing the rate of anastomotic leakage.

Aortic inflation with agar injection is a useful method of cadaveric preparation which creates a mediastinal anatomy that better mimics the living body for surgical training.

In cadavers, even Thiel-embalmed cadavers, the arteries (especially the thoracic aorta) are extremely collapsed. This is in marked contrast to the state of the arteries in a living body. Aortic inflation is necessary to improve this unfavorable situation for anatomical observation or dissection. To inflate the aorta, we injected 500 ml of hot liquid agar into the aorta using a 18-Fr catheter inserted into the common femoral artery and subclavian artery. The injected agar then rapidly cools to room temperature and solidifies. As a result, the thoracic aorta remains sufficiently and constantly inflated in the mediastinum. This method is not only easy and inexpensive, but also useful and effective for achieving a life-like anatomy in cadavers used in surgical training for operations involving mediastinal organs, with the exception of the heart and great vessels.

The usefulness of a bilateral trans-cervical pneumomediastinal approach for mediastinoscopic radical esophagectomy: a right transcervical approach is an available option.

OBJECTIVE: We investigated the merits and demerits of right cervical open surgery with right trans-cervical pneumomediastinal approach in mediastinoscopic esophagectomy. METHODS: Ten thoracic esophageal cancer patients were treated using this approach. Under pneumomediastinum via a right neck incision, the right cervical and upper mediastinal paraesophageal lymph nodes were dissected. The left recurrent nerve lymph nodes were dissected using a left trans-cervical pneumomediastinal approach. The subaortic arch to the left tracheobronchial lymph nodes was dissected with a combined right and left trans-cervical crossover approach. RESULTS: The average number of dissected lymph nodes among the right cervical and upper mediastinal paraesophageal lymph nodes identified with a right cervical open/right trans-cervical mediastinoscopic/right thoracoscopic approach was 3.2/4.0/0.6, respectively. The average number of dissected lymph nodes among the subaortic arch to the left tracheobronchial lymph nodes with a right trans-cervical mediastinoscopic/right thoracoscopic approach was 1.5/0.6, respectively. These findings indicate that, without using the right trans-cervical pneumomediastinal approach, it might be impossible to successfully remove some of the right cervical and upper mediastinal paraesophageal lymph nodes and the subaortic arch to the left tracheobronchial lymph nodes lymph nodes. Regarding surgical complications, one case of bilateral recurrent nerve palsy as well as two cases on the right and two cases on the left were noted. CONCLUSIONS: Although the rate of recurrent nerve palsy should still be reduced, a bilateral (especially right-sided) trans-cervical pneumomediastinal approach is an available option for achieving sufficient upper mediastinal lymph node dissection and esophagectomy.

Mid- and long-term outcomes of endoscopic resection for submucosal esophageal cancer types pT1b-SM1 and pT1b-SM2.

Background and study aims Endoscopic submucosal dissection (ESD) and endoscopic mucosal resection (EMR) are promising therapeutic options for early esophageal cancer (EC). The factors that can affect mid- and long-term survival in patients with submucosal EC (SM1 and SM2) have not been described in the literature. We aim to describe clinicopathological outcomes and factors that can affect the mid- and long-term survival in patients with resected submucosal tumors. Patients and methods We performed a retrospective analysis of patients who underwent endoscopic resection (ER) for submucosal tumors over a 20-year period. The final study population included 119 cases with 137 lesions. Information was collected according to the Japanese Classification of Esophageal Cancer 11-edition and factors affecting survival for 2 and 5 years after ER were analyzed. Results EMR was performed in 99 cases (72.3 %), ESD in 38 cases (27.7 %). There were no significant complications. Two- and 5-year survival rates were 91 % and 82 %, respectively. Mean age was 67.22 years (±â€Š9.49 years), mortality caused by EC occurred in 13 cases (11 %). Factors that had a significant impact on long-term survival were age > 65 years ( P  = 0.0026), number of resected specimens ( P  = 0.0031), presence of another progressive disease (not EC) ( P  ≤ 0.001), recurrence ( P  = 0.0002), and relation between histopathological positive vertical margin and recurrence ( P  = 0.0112). Conclusions ER is viable treatment for esophageal submucosal cancer, selection between ESD/EMR can depend on tumor size and patient condition, and en bloc ER is the recommended technique for submucosal tumors. Long-term survival factors were identified.

CHAC1 overexpression in human gastric parietal cells with Helicobacter pylori infection in the secretory canaliculi.

BACKGROUND: Cation transport regulator 1 (CHAC1), a newly discovered enzyme that degrades glutathione, is induced in Helicobacter pylori (H. pylori)-infected gastric epithelial cells in culture. The CHAC1-induced decrease in glutathione leads to an accumulation of reactive oxygen species and somatic mutations in TP53. We evaluated the possible correlation between H. pylori infection and CHAC1 expression in human gastric mucosa. MATERIALS AND METHODS: Both fresh-frozen and formalin-fixed paraffin-embedded tissue samples of gastric mucosa with or without H. pylori infection were obtained from 41 esophageal cancer patients that underwent esophago-gastrectomy. Fresh samples were used for real-time polymerase chain reaction for H. pylori DNA and CHAC1 mRNA, and formalin-fixed samples were used for immunohistochemistry with anti-CHAC1 and anti-H. pylori monoclonal antibodies. Double-enzyme or fluorescence immunohistochemistry and immuno-electron microscopy were used for further analysis. RESULTS: Significant CHAC1 overexpression was detected in H. pylori-infected parietal cells that expressed the human proton pump/H,K-ATPase α subunit, whereas a constitutively low level of CHAC1 mRNA expression was observed in the other samples regardless of the H. pylori infection status, reflecting the weak CHAC1 expression detected by immunohistochemistry in the fundic-gland areas. Immuno-electron microscopy revealed intact H. pylori cells in the secretory canaliculi of infected parietal cells. Some parietal cells exhibited positive nuclear signals for Ki67 in the neck zone of the gastric fundic-gland mucosa with H. pylori infection. CONCLUSION: Cation transport regulator 1 overexpression in H. pylori-infected parietal cells may cause the H. pylori-induced somatic mutations that contribute to the development of gastric cancer.

A feasibility study of mediastinoscopic radical esophagectomy for thoracic esophageal cancer from the viewpoint of the dissected mediastinal lymph nodes validated with thoracoscopic procedure: a prospective clinical trial.

PURPOSE: A prospective trial evaluated the feasibility and safety of "mediastinoscopic esophagectomy with lymph node dissection" (MELD). METHODS: Eligible patients had thoracic esophageal squamous cell carcinoma, excluding T4, a bulky primary lesion or distant metastasis. Ten patients were enrolled and treated between September 2015 and March 2018. Additionally, to verify the integrity of the mediastinal lymph node dissection, thoracoscopic observation and lymph node dissection were followed. The primary end point was the integrity of mediastinal lymph node dissection. The secondary end points were the short-term outcomes, including mortality and morbidity. RESULTS: The median number of dissected lymph nodes in the upper mediastinal to cervical region and middle to lower mediastinal region by mediastinoscopy/thoracoscopy was 27/0.5 and 11.5/0, respectively. The median total operation time was 615 min, the median bleeding amount was 476 ml, and the median postoperative hospital stay was 15.5 days. Regarding complications of more than grade III according to the Clavien-Dindo classification, four had sputum excretion difficulty, one had pneumothorax and one had bilateral recurrent nerve palsy, but none required conversion to thoracotomy, and no operative deaths occurred. CONCLUSION: Although the rate of recurrent nerve palsy still should be reduced, our mediastinoscopic lymphadenectomy technique is closely similar to radical esophagectomy.

Comparative Study of Predictive Mortality Scores in Esophagectomy with Three-Field Lymph Node Dissection in Patients with Esophageal Cancer.

BACKGROUND/AIM: Esophagectomy is still the best therapeutic option for curing resectable esophageal cancer (EC). Radical surgical resection with three-field lymphadenectomy (3FLD) is a potentially curative treatment option. We compared the predictive accuracy of 5 different scores in patients with EC who underwent 3FLD. METHODS: Five years' worth of medical records in a single institution were analyzed (January 2010 to January 2015) from 311 patients who underwent esophagectomy for EC. We selected 191 in whom 3FLD was performed. Mortality was calculated based on 5 predictive scores. Outcomes measures were intraoperative mortality, 30-day mortality, and 1- and 2-year mortality after surgery. RESULTS: Intraoperative mortality and 30-day mortality after surgery was 0%; 1 and 2-year mortality were 19.8 and 31.4%, respectively. The area under the curve showed poor discriminatory power for all 5 scores (<0.7). In one-way analysis of variance, for 1 year mortality, Portsmouth-Physiological and Operative Severity Score for mortality (P-Possum) was significant (p = 0.0424); in a multivariable analysis for 2-year mortality, P-Possum (p < 0.0001) remained significant. CONCLUSION: There is no accurate prognosis score for esophagectomy in patients who undergo high-risk procedures like 3FLD. New scores are needed to predict the mortality after 3FLD with good discriminatory power. Independent factors affect survival and may function as the baseline for obtaining a new accurate mortality score.

Detection of Second Primary Malignancies of the Esophagus and Hypophraynx in Oral Squamous Cell Carcinoma Patients.

OBJECTIVE: To assess the usefulness of modified esophagogastroduodenoscopy (EGD) for the detection of second primary malignancies of the esophagus or hypopharynx in patients with oral squamous cell carcinoma and determine the association between the oral lesion subsite and esophageal or hypopharyngeal lesion occurrence. STUDY DESIGN: Retrospective review. METHODS: In total, 166 patients with oral squamous cell carcinoma without any established symptoms of esophageal or hypopharyngeal squamous cell carcinoma underwent modified EGD based on the Valsalva maneuver and U-turn method, image-enhanced endoscopy, and chromoendoscopy using Lugol's iodine for diagnosis. All suspected lesions were biopsied to determine the clinical stages and duplication rates. Odds ratios for the occurrence of duplicate lesions according to the oral lesion subsite were determined. RESULTS: In total, 37 esophageal and 16 hypopharyngeal lesions were detected. According to the Union for International Cancer Control/American Joint Committee on Cancer classification (2009), 75.7% and 5.4% esophageal lesions were classified as stage IA and IB, respectively, and 50% and 18.8% hypopharyngeal lesions as stage II and stage I, respectively. Approximately 59.1% and 50% esophageal and hypopharyngeal lesions, respectively, were successfully treated by endoscopic resection. Oral lesions involving the floor of the mouth were more frequently accompanied by second primary malignancies of the esophagus or hypopharynx. CONCLUSIONS: Modified EGD is an effective noninvasive technique for early diagnosis and treatment of second primary malignancies of the esophagus and hypopharynx in patients with oral squamous cell carcinoma. In particular, patients with floor of the mouth lesions need close monitoring for hypopharyngeal and esophageal lesions. LEVEL OF EVIDENCE: 3b.

Histological study of the thin membranous structure made of dense connective tissue around the esophagus in the upper mediastinum.

BACKGROUND: The structure of the fascia in upper mediastinum has already been reported from gross anatomical viewpoints by Sarrazin. But it is necessary to understand meticulous anatomy for thoracoscopic or mediastinoscopic surgery. So herein, we investigate histologically the thin membranous structure made of dense connective tissues. METHODS: Semi-sequential transverse sections of the mediastinum were obtained from three cadavers. Hematoxylin and eosin staining, Elastica van Gieson staining, and Masson trichrome staining were performed to identify the presence and location of the thin membranous structure made of dense connective tissues. RESULTS: The "visceral sheath" and "vascular sheath," as previously described by Sarrazin, were observed histologically. These two thin membranous structures do not surround the esophagus and trachea cylindrically. In addition, the "visceral sheath" on the right side of the upper mediastinum was unclear in comparison to the left side. The "visceral sheath" (on the left side) gradually became unclear, and seemed to almost disappear; the esophagus was found to be very close to the thoracic duct on the caudal side of the bifurcation of the trachea. Although the left recurrent nerve was located inside the "visceral sheath" in all cadavers, the left recurrent nerve lymph nodes were located inside the "visceral sheath" in cadaver 1 and between the "visceral sheath" and "vascular sheath" in cadaver 3. CONCLUSION: The "visceral sheath" around the esophagus in the upper mediastinum was histologically demonstrated; however, the findings were not constant.

Anatomical study of the left superior mediastinal lymphatics for tracheal branches of left recurrent laryngeal nerve-preserving mediastinoscope-assisted surgery in esophageal cancer.

PURPOSE: Curative treatment of esophageal cancer requires meticulous superior mediastinal lymphadenectomy, in addition to esophagectomy, because superior mediastinal lymph node metastases are common in esophageal cancer. When preserving the tracheal branches of the left recurrent laryngeal nerve (RLN), good anatomical understanding is required for confirmation of the positional relationships between the courses of lymphatic vessels, lymph node distribution, and the left RLN and its tracheal branches. We performed a detailed anatomical examination of these relationships. METHODS: Macroscopic anatomical observation and histological examination was performed on cadavers. In addition to hematoxylin and eosin staining, immunostaining using antipodoplanin antibody D2-40 (podoplanin) was performed to identify the lymphatic vessels. RESULTS: The tracheal branches of the left RLN were clearly observed, but no lymphatic vessels crossing the ventral or dorsal side of the branches were identified either macro-anatomically or histologically. CONCLUSION: No complex lymphatic network structure straddling the plane composed of tracheal branches of the left RLN was found in the left superior mediastinum. This suggests that dissection of the lymph nodes around the left RLN via the pneumomediastinum method using the left cervical approach may allow preservation of the tracheal branches of the left RLN by maintaining dissection accuracy.