The normal configuration and interindividual differences in intramural lymphatic vessels of the esophagus

Lymphatic flow mapping using near-infrared fluorescence imaging with indocyanine green helps to predict lymph node metastasis intraoperatively in patients with esophageal or esophagogastric junction cancer not treated with neoadjuvant chemotherapy

BACKGROUND

Lymphatic flow mapping using near-infrared fluorescence (NIR) imaging with indocyanine green (ICG) has been used for the intraoperative prediction of lymph node metastasis in esophageal or esophagogastric junction cancer. However, a consistent method that yields sufficient diagnostic quality is yet to be confirmed. This study explored the diagnostic utility of our newly established lymphatic flow mapping protocol for predicting lymph node metastasis in patients with esophageal or esophagogastric junction cancer.

METHODS

We injected 0.5 mL of ICG (500 μg/mL) into the submucosal layer at four peritumoral points on the day before surgery for 54 patients. We performed lymphatic flow mapping intraoperatively using NIR imaging. After determining the NIR status and presence of metastases, evaluable lymph node stations on in vivo imaging and all resected lymph nodes were divided into four categories: ICG+meta+ (true positive), ICG+meta- (false positive), ICG-meta+ (false negative), and ICG-meta- (true negative).

RESULTS

The distribution of ICG+ and meta+ lymph node stations differed according to the primary tumor site. Sensitivity and specificity for predicting meta+ lymph nodes among ICG+ ones were 50% (95% CI 41-59%) and 75% (73-76%), respectively. Predicting meta+ lymph node stations among ICG+ stations improved these values to 66% (54-77%) and 77% (74-79%), respectively. Undergoing neoadjuvant chemotherapy was an independent risk factor for having meta+ lymph nodes with false-negative diagnoses (odds ratio 4.82; 95% CI 1.28-18.19). The sensitivity of our technique for predicting meta+ lymph nodes and meta+ lymph node stations in patients who did not undergo neoadjuvant chemotherapy was 79% (63-90%) and 83% (61-94%), respectively.

CONCLUSION

Our protocol potentially helps to predict lymph node metastasis intraoperatively in patients with esophageal or esophagogastric junction cancer undergoing esophagectomy who did not undergo neoadjuvant chemotherapy.

Prediction of lymph node metastasis in early esophageal cancer

BACKGROUND

Given the poor prognosis of patients with lymph node metastasis, estimating the lymph node status in patients with early esophageal cancer is crucial. Indicators that could be used to predict lymph node metastasis in early esophageal cancer have been reported in many recent studies, but no recent studies have included a review of this subject.

AIM

To review indicators predicting lymph node metastasis in early esophageal squamous cell carcinoma (ESCC) and early esophageal adenocarcinoma (EAC).

METHODS

We searched PubMed with "[early esophageal cancer (Title/Abstract)] and [lymph node (Title/Abstract)]" or "[early esophageal carcinoma (Title/Abstract)] and [lymph node (Title/Abstract)]" or "[superficial esophageal cancer (Title/Abstract)] and [lymph node (Title/Abstract)]." A total of 29 studies were eligible for analysis.

RESULTS

Preoperative imaging (size), serum markers (microRNA-218), postoperative pathology and immunohistochemical analysis (depth of invasion, tumor size, differentiation grade, lymphovascular invasion, neural invasion, expression of PIM-1 < 30%) were predictive factors for lymph node metastasis in both early ESCC and EAC. Serum markers (thymidine kinase 1 ≥ 3.38 pmol/L; cytokeratin 19 fragment antigen 21-1 > 3.30 ng/mL; stathmin-1) and postoperative pathology and immunohistochemical analysis (overexpression of cortactin, mixed-lineage leukaemia 2, and stanniocalcin-1) were predictive for lymph node metastasis in early ESCC. Transcription of CD69, myeloid differentiation protein 88 and toll-like receptor 4 and low expression of olfactomedin 4 were predictive of lymph node metastasis in early EAC. A total of 6 comprehensive models for early ESCC, including logistic regression model, nomogram, and artificial neural network (ANN), were reviewed. The areas under the receiver operating characteristic curve of these models reached 0.789-0.938, and the ANN performed best. As all these models relied on postoperative pathology, further models focusing on serum markers, imaging and immunohistochemical indicators are still needed.

CONCLUSION

Various factors were predictive of lymph node metastasis in early esophageal cancer, and present comprehensive models predicting lymph node metastasis in early ESCC mainly relied on postoperative pathology. Further studies focusing on serum markers, imaging and immunohistochemical indicators are still in need.

Mechanisms of esophageal cancer metastasis and treatment progress

Esophageal cancer is a prevalent tumor of the digestive tract worldwide. The detection rate of early-stage esophageal cancer is very low, and most patients are diagnosed with metastasis. Metastasis of esophageal cancer mainly includes direct diffusion metastasis, hematogenous metastasis, and lymphatic metastasis. This article reviews the metabolic process of esophageal cancer metastasis and the mechanisms by which M2 macrophages, CAF, regulatory T cells, and their released cytokines, including chemokines, interleukins, and growth factors, form an immune barrier to the anti-tumor immune response mediated by CD8+ T cells, impeding their ability to kill tumor cells during tumor immune escape. The effect of Ferroptosis on the metastasis of esophageal cancer is briefly mentioned. Moreover, the paper also summarizes common drugs and research directions in chemotherapy, immunotherapy, and targeted therapy for advanced metastatic esophageal cancer. This review aims to serve as a foundation for further investigations into the mechanism and management of esophageal cancer metastasis.

Anatomy of lymphatic drainage of the esophagus and lymph node metastasis of thoracic esophageal cancer

The lymphatic drainage of the inner layers (mucosa and submucosa) and the outer layers (muscularispropria and adventitia) of the thoracic esophagus is different. Longitudinal lymphatic vessels and long drainage territory in the submucosa and lamina propria should be the bases for bidirectional drainage and direct drainage to thoracic duct and extramural lymph nodes (LN). The submucosal vessels for direct extramural drainage are usually thick while lymphatic communication between the submucosa and intermuscular area is usually not clearly found, which does not facilitate transversal drainage to paraesophageal LN from submucosa. The right paratracheal lymphatic chain (PLC) is well developed while the left PLC is poorly developed. Direct drainage to the right recurrent laryngeal nerve LN and subcarinal LN from submucosa has been verified. Clinical data show that lymph node metastasis (LNM) is frequently present in the lower neck, upper mediastinum, and perigastric area, even for early-stage thoracic esophageal cancer (EC). The lymph node metastasis rate (LNMR) varies mainly according to the tumor location and depth of tumor invasion. However, there are some crucial LN for extramural relay which have a high LNMR, such as cervical paraesophageal LN, recurrent laryngeal nerve LN, subcarinal LN, LN along the left gastric artery, lesser curvature LN, and paracardial LN. Metastasis of thoracic paraesophageal LN seems to be a sign of more advanced EC. This review gives us a better understanding about the LNM and provides more information for treatments of thoracic EC.

The impact of adjuvant therapies on patient survival and the recurrence patterns for resected stage IIa-IVa lower thoracic oesophageal squamous cell carcinoma

Background

This study evaluated the impact of adjuvant therapies on patient survival and disease recurrence patterns to identify an effective adjuvant therapy for resected lower thoracic oesophageal squamous cell carcinoma (LTESCC).

Methods

Clinical data of 127 patients with stage IIa-IVa LTESCC with a minimum 2-year follow-up after oesophagectomy were analysed. The survival and recurrence patterns were compared among patients who received adjuvant radiotherapy, adjuvant chemotherapy, adjuvant chemoradiotherapy, or surgery alone.

Results

Eighty-eight patients (69.3%) were identified as having disease recurrence. The regional lymph node recurrence rate was 57.5%, and the recurrence rates were high in the lower neck, upper mediastinum, and upper abdomen. Compared to surgery alone, adjuvant radiotherapy or chemoradiotherapy significantly decreased the recurrence rate (p < 0.05). Adjuvant chemoradiotherapy significantly improved overall survival, disease-free survival, and locoregional recurrence-free survival compared to surgery alone (p = 0.01, 0.01, and 0.00, respectively). Pathologically positive lymph nodes (PPLNs) in the lower mediastinum represented a potential risk factor for cervical recurrence (HR 2.97, 95%CI 1.19–7.39). Multivariable analysis showed that postoperative radiotherapy (HR 0.30, 95%CI 0.13–0.68) and PPLNs in the upper mediastinum (HR 3.72, 95%CI 1.30–10.67) were independent risk factors for upper mediastinal recurrence, while postoperative radiotherapy (HR 0.37, 95%CI 0.16–0.85) and PPLNs in the abdomen (HR 2.57, 95%CI 1.12–5.92) were independent risk factors for abdominal recurrence.

Conclusion

Adjuvant chemoradiotherapy was the most effective adjuvant therapy for resected stage IIa-IVa LTESCC. The lower neck, upper mediastinum, and upper abdomen were high-risk regions for postoperative radiotherapy. The regions of PPLNs may be important factors for individual targets.

Clinical significance of esophageal invasion length for the prediction of mediastinal lymph node metastasis in Siewert type II adenocarcinoma: A retrospective single-institution study

AIM

This study investigated whether esophageal invasion length (EIL) of a tumor from the esophagogastric junction could be a possible indicator of mediastinal lymph node metastasis and survival in patients with Siewert type II adenocarcinoma.

METHODS

One hundred and sixty-eight patients with Siewert type II tumor who underwent surgery were enrolled. Metastatic stations and recurrent lymph node sites were classified into cervical, upper/middle/lower mediastinal, and abdominal zones. EIL was correlated with overall metastasis or recurrence in individual zones and with survival.

RESULTS

Siewert type II patients with an EIL of more than 25 mm (>25 mm EIL group) had a higher incidence of overall metastasis or recurrence in the upper and middle mediastinal zones than those with an EIL of less than or equal to 25 mm (≤25 mm EIL group) (P = .001 and P < .001). Disease-free and overall survival in the >25 mm EIL group were significantly lower than those of the ≤25 mm EIL group (P < .001). None of the Siewert type II patients with metastasis or recurrence in the upper and middle mediastinal zones survived for more than 5 years. Only an EIL of more than 25 mm was a significant preoperative predictor of overall metastasis or recurrence in the upper and middle mediastinal zones (odds ratio, 8.85; 95% CI, 2.31-33.3; P = .001).

CONCLUSION

A multimodal-therapeutic strategy should be investigated in Siewert type II patients once the tumor has invaded more than 25 mm to the esophageal wall.

Elucidation of the Anatomical Mechanism of Nodal Skip Metastasis in Superficial Thoracic Esophageal Squamous Cell Carcinoma

Background

Lymph node metastasis (LNM) is a standard mechanism of cancer progression in esophageal squamous cell carcinoma (ESCC). We aimed to clarify the anatomical mechanism of skip nodal metastasis to mediastinal zones by analyzing the relationship between LNM to sentinel zones and lymphatic vessel counts in the muscle layer adjacent to the outer esophagus.

Methods

We examined the surgical records of 287 patients with ESCC who underwent potentially curative surgery (three-field lymphadenectomy) and whole esophagi, including pharynges and stomachs from 10 cadavers, to determine the number of lymphatic vessels in the intra-outer longitudinal muscle layer adjacent to the outer esophagus of the cervical (Ce), upper thoracic, middle thoracic (Mt), lower thoracic (Lt), and abdominal esophagi (Ae).

Results

The frequency of LNM to the middle mediastinal and supraclavicular zones, including the Mt and Ce, respectively, was lower than to the upper and lower mediastinal and abdominal zone in patients with superficial and advanced thoracic ESCC. In cadavers, the lymphatic vessel counts of the intra-outer longitudinal muscle layer in the Mt and Ce were significantly lower than those of the Lt and Ae, suggesting that lymphatic flow toward the outside of the Mt and Ce was not more abundant than to other sites.

Conclusion

Our anatomical data suggested that the absence of intra-muscle lymphatic vessels in the middle mediastinal and supraclavicular zones causes skip LNM in patients with thoracic ESCC. Thus, standard esophagectomy with lymph node dissection, including distant zones, may be appropriate for treating patients with superficial thoracic ESCC.

Electronic supplementary material

The online version of this article (10.1245/s10434-018-6390-0) contains supplementary material, which is available to authorized users.

Clinicopathologic Features of Submucosal Esophageal Squamous Cell Carcinoma

BACKGROUND

The prognoses of submucosal esophageal squamous cell carcinoma patients vary. Patients with favorable prognoses may receive less invasive or nonsurgical interventions, whereas patients with poor prognoses or advanced esophageal cancer may require aggressive treatments. We sought to identify prognostic factors for patients with submucosal esophageal squamous cell carcinoma, focusing on lymph node metastasis and recurrence.

METHODS

We included 137 submucosal esophageal squamous cell carcinoma patients who had undergone transthoracic esophagectomy with systematic extended lymph node dissection. Submucosal tumors were classified as SM1, SM2, and SM3 according to the depth of invasion. Prognostic factors were determined by univariable and multivariable analyses.

RESULTS

Lymph node metastasis was observed in 18.8%, 30.5%, and 50.0% of SM1, SM2, and SM3 cases, respectively. The overall 5-year recurrence rate was 21.9%; the rates for SM1, SM2, and SM3 tumors were 9.4%, 18.6%, and 34.8%, respectively. The SM1 tumors all recurred locoregionally; distant metastasis occurred in SM2 and SM3 cases. The 5-year overall survival rates were 83%, 77%, and 59% for SM1, SM2, and SM3 cases, respectively. On univariable analysis, lymph node metastasis, depth of submucosal invasion (SM3 versus SM1/2), and tumor location (upper thoracic versus mid/lower thoracic) were poor prognostic factors for overall survival. Multivariable Cox regression analyses identified depth of submucosal invasion (hazard ratio 2.51, 95% confidence interval: 1.37 to 4.61) and tumor location (hazard ratio 2.43, 95% confidence interval: 1.18 to 4.63) as preoperative prognostic factors.

CONCLUSIONS

Tumor location (upper thoracic) and infiltration (SM3) are the worse prognostic factors of submucosal esophageal squamous cell carcinoma, but lymph node metastasis is not a predictor of poorer prognosis.

Tumor location is a risk factor for lymph node metastasis in superficial Barrett's adenocarcinoma

BACKGROUND AND STUDY AIMS

Endoscopic treatment is indicated for superficial Barrett's adenocarcinoma (BA) with a negligible risk of lymph node metastasis (LNM). However, risk factors associated with LNM in superficial BA are still not well characterized. The aim of the current study was to clarify risk factors for LNM of superficial BA.

PATIENTS AND METHODS

A retrospective study was conducted in 87 consecutive patients with BA that was resected at National Cancer Center Hospital, Tokyo, Japan between 1990 and 2013. We assessed tumor size, macroscopic type, histological type, tumor depth of invasion, lymphovascular invasion and tumor location to analyze factors associated with LNM. Tumor location was classified into following 2 groups according to Siewert classification: 1) BA of the esophagogastric junction (EGJ-BA) as those having their center within 1 cm proximal from the EGJ; and 2) Esophageal-BA as those having their center at 1 cm or more proximal to the EGJ. EGJ was defined as distal end of the palisade vessels.

RESULTS

 LNM was detected in 10 (11 %) patients. Univariable analysis revealed that tumor size, tumor depth of invasion, histological type of mixed differentiated and undifferentiated-type adenocarcinoma, lymphovascular invasion and tumor location of esophageal-BA were significantly associated with LNM. Multivariable analysis revealed that tumor location of esophageal-BA [odds ratio 7.8 (95 %CI: 1.3 - 48.1)] was a potential risk factor for LNM.

CONCLUSIONS

The current study demonstrated that tumor location is a potential risk factor for LNM in BA. Therefore, indications for endoscopic treatment of esophageal-BA and EGJ-BA could be different.

Characteristics of Postoperative Recurrence in Lymph Node-Negative Superficial Esophageal Carcinoma

BACKGROUND

This study aimed to evaluate the recurrence rates, timings, locations, and risk factors, and survival in patients with lymph node-negative superficial esophageal squamous cell carcinomas (ESCCs).

METHODS

We investigated 167 patients with pathological T1 thoracic ESCC who underwent curative esophagectomy with lymphadenectomy between 1986 and 2013. They were classified into lymph node-negative and lymph node-positive groups, each of which included 15 relapsed patients. The recurrence rates, timings, locations, and risk factors, and survival were examined retrospectively.

RESULTS

Significantly better recurrence (12.4 %) and the 5-year overall survival (85.7 %) rates were seen in patients with node-negative superficial ESCC compared with those with node-positive superficial ESCC. Relapsed patients with node-negative superficial ESCC showed a 5-month delay in the time to recurrence compared with relapsed patients with node-positive superficial ESCC, but the recurrence locations were similar. Upper thoracic tumors and the presence of lymph node metastases were independent risk factors for recurrence in superficial ESCC patients, but we did not determine any risk factors in patients who were node negative only. The 5-year overall survival rates did not differ between relapsed node-negative and node-positive patients. Furthermore, the mean times to death and the survival rates from recurrence to death were similar in the node-negative (20.3 months and 9.3 %, respectively) and in the node-positive patients (19.1 months and 13.6 %, respectively) who had relapsed.

CONCLUSIONS

Node-negative and node-positive superficial ESCC patients should be followed up similarly, because when recurrences occur, the prognoses and the times to death are similar in node-negative and node-positive superficial ESCC patients.

Distribution of CD10-positive epithelial and mesenchymal cells in human mid-term fetuses: a comparison with CD34 expression

CD10, a marker of immature B lymphocytes, is expressed in the developing epithelium of mammary glands, hair follicles, and renal tubules of human fetuses. To assess mesenchymal and stromal expression of CD10, we performed immunohistochemical assays in whole body sections from eight fetuses of gestational ages 15-20 weeks. In addition to expression in urinary tract and intestinal epithelium, CD10 was strongly expressed at both gestational ages in fibrous tissues surrounding the airways from the larynx to lung alveoli, in the periosteum and ossification center, and in the glans of external genitalia. CD10 was not expressed, however, in other cavernous tissues. These findings suggest that mesenchymal, in addition to epithelial cells at specific sites, are likely to express CD10. The glomeruli, alveoli, and glans are all end products of budding or outgrowth processes in the epithelium or skin. However, in contrast to the CD34 marker of stromal stem cells, CD10 was not expressed in vascular progenitor cells and in differentiated vascular endothelium. The alternating pattern of CD10 and CD34 expression suggests that these factors play different roles in cellular differentiation and proliferation of the kidneys, airway and external genitalia.

Mucosal lymphatic vessels of the esophagus distant from the cancer margin: morphometrical analysis using 27 surgically removed specimens of squamous cell carcinoma located in the upper or middle thoracic esophagus

PURPOSE

To clarify the configuration of the esophageal mucosal lymphatics distant from cancer using D2-40 immunohistochemistry.

METHODS

D2-40 immunohistochemistry for human lymphatic epithelium was performed at sites about 10 cm anal from the pathologically examined margin of upper or mid- thoracic squamous cell carcinoma (27 patients). We measured the entire length of mucosal lymphatic vessels within a x10 objective field (1.2 mm along the muscularis mucosae).

RESULTS

The present morphometrical study demonstrated significant individual differences in the amount of mucosal lymphatic vessels, within a range of more than 10-fold (8.4 mm-0.8 mm within an objective field). However, the difference in length of the mucosal lymphatic epithelium did not correlate with either N-factor, T-factor including cancer depth or prognosis.

CONCLUSION

A higher density of pre-existing mucosal lymphatic vessels may not always be correlated with larger numbers of nodal metastases. Lymphatic proliferation or dilation induced by cancer seems to occur irrespective of whether pre-existing vessels are rich or sparse.

Esophageal submucosa: the watershed for esophageal cancer

OBJECTIVES

Submucosal esophageal cancers (pT1b) are considered superficial, implying good survival. However, some are advanced, metastasizing to regional lymph nodes. Interplay of cancer characteristics and lymphatic anatomy may create a watershed, demarcating low-risk from high-risk cancers. Therefore, we characterized submucosal cancers according to depth of invasion and identified those with high likelihood of lymph node metastases and poor survival.

METHODS

From 1983 to 2010, 120 patients underwent esophagectomy for submucosal cancers at Cleveland Clinic. Correlations were sought among cancer characteristics (location, dimensions, histopathologic cell type, histologic grade, and lymphovascular invasion [LVI]), and their associations with lymph node metastasis were identified by logistic regression. Associations with mortality were identified by Cox regression.

RESULTS

As submucosal invasion increased, cancer length (P < .001), width (P < .001), area (P < .001), LVI (P = .007), and grade (P = .05) increased. Invasion of the deep submucosa (P < .001) and LVI (P = .06) predicted lymph node metastases: 45% (23/51) of deep versus 10% (3/29) of middle-third and 7.5% (3/40) of inner-third cancers had lymph node metastases, as did 46% (12/26) with LVI versus 18% (17/94) without. Older age and lymph node metastases predicted worse 5-year survival: 94% for younger pN0 patients, 62% for older pN0 patients, and 36% for pN1-2 patients regardless of age.

CONCLUSIONS

Submucosal cancer characteristics and lymphatic anatomy create a watershed for regional lymph node metastases in the deep submucosa. This previously unrecognized divide distinguishes superficial submucosal cancers with good survival from deep submucosal cancers with poor survival. Aggressive therapy of more superficial cancers is critical before submucosal invasion occurs.

Salvage lymphadenectomy for cervical lymph node recurrence after esophagectomy for squamous cell carcinoma of the thoracic esophagus

Prognosis of patients with recurrent esophageal cancer is usually unsatisfactory. We have successfully treated five patients with cervical node recurrence after esophagectomy with multimodal treatment including salvage lymphadenectomy. In order to clarify the efficacy of salvage surgery for cervical node recurrence, we have reviewed the clinical course and prognosis of these patients. From August 2004 to December 2007, 30 patients with 33 recurrent sites were treated in the Department of Surgery, Iizuka Hospital. Among these patients, there were five patients with recurrence limited within the cervical nodes. Salvage cervical lymphadenectomy was performed for all five patients. Curative resection was achieved in four patients and reduction surgery followed by planned chemoradiotherapy was performed in another patient. All stations including the suspicious node were dissected and a partial sternotomy was added for one patient whose recurrent tumor was located in the right recurrent nerve node. There was no mortality and one minor complication (subcutaneous hemorrhage) was observed. Median duration of hospital stay was 7 days. Adjuvant chemotherapy was performed for all patients. Median follow-up period was 54 months and all patients are alive without relapse of the disease. Salvage cervical lymphadenectomy is a safe and effective treatment for patients with cervical node recurrence after esophagectomy.

Fetal topographical anatomy of the upper abdominal lymphatics: its specific features in comparison with other abdominopelvic regions

Using semiserial sections from 19 human fetuses of 8-30 weeks gestation, we examined the topohistology of the upper abdominal lymphatics and compared it with that of the lower abdominal and pelvic lymphatics. The upper abdominal lymphatics were characterized by an intimate relationship with the peritoneal lining, a common mesentery for the celiac trunk and superior mesenteric artery (SMA). Lymphatic connections from the upper abdominal viscera to the paraaortic and paracaval areas followed two routes: (1) from the intestinal mesentery, along the peritoneum on the left aspect of the proximal SMA, via the chain of lymph follicles (LFs) lying along the retropancreatic fusion fascia, to drain into the LFs around the left renal vein; (2) from sites along the peritoneum on the posterior wall of the omental bursa, via the root of the hepatoduodenal ligament, to drain into LFs around the vena cava. The development of these two posterior drainage routes seemed to be promoted by the peritoneum or a peritoneal remnant (i.e., fusion fascia) attaching to the great vessels, and inhibited or impeded by the developing nerves and diaphragm. No paraaortic, paracaval, or pelvic LFs lay along the peritoneum. The pelvic LFs were usually located along the bundle of lymphatic vessels originating from the femoral canal.

The esophageal wall

The esophagus spans three body cavities and has no mesentery, continually borrowing or sharing vessels, lymphatics, and nerves with associated organs. However, constant along this path is an intricate mural structure. An understanding of the esophageal wall, its blood supply, lymphatic drainage, and innervation is essential for successful esophageal surgery.

Fetal anatomy of peripheral lymphatic vessels: a D2-40 immunohistochemical study using an 18-week human fetus (CRL 155 mm)

We demonstrated fetal peripheral lymphatic vessels (LVs) using D2-40 immunohistochemistry in a whole female fetus (18 weeks of gestation, CRL 155 mm) except for the head. There were abundant LVs in the thyroid gland, lung, stomach, small intestine, rectum and pancreas, whereas no LVs were seen in the parathyroid gland, spleen and adrenal cortex. In the liver, except for the gallbladder bed, LVs were still restricted to around hilar thick portal veins and around the hepatic vein terminals. Subcutaneous LVs were well developed throughout the body even in areas where no or few perforating LVs connected with the deep LVs. The diaphragm contained abundant, dilated LVs in the pleural half of its thickness. LVs were also seen not only along supplying arteries of muscles and cartilage but also along the epimysium and perichondrium. LVs ran in a space between the obliquus internus and transversus abdominis but not between the obliquus internus and obliquus externus. Some tight connective tissues such as the sacrotuberous ligament contained abundant LVs. The intervertebral foramen contained a lymphatic plexus. The present observations provide a better understanding of peripheral lymphatic development. The fetal lymphatic morphology seems not to represent a mini-version of the adult morphology.

Smooth-to-striated muscle transition in human esophagus: an immunohistochemical study using fetal and adult materials

BACKGROUND

A craniocaudal transition from smooth to striated muscle occurs in the fetal mouse esophagus muscularis propria, until finally the entire muscle component becomes striated. Although no such investigation has been conducted using human fetuses, the transition appears to be incomplete.

METHODS

In horizontal sections of 10 human fetuses between 9 and 16 weeks of gestation, we identified immunoreactivity for smooth muscle actin (SMA), striated muscle myosin heavy chain (MyH), desmin, PGP9.5, S100 protein, c-kit, and CD68 in the thoracic esophagus. The TUNEL method was used to identify apoptosis. For comparison, the same immunohistochemistry was conducted using 10 adult esophaguses.

RESULTS

In fetuses at all stages examined, a transition zone was found in the upper thoracic esophagus that was attached to the middle one-third of the trachea. In the transition zone, the MyH-positive longitudinal muscle fibers were surrounded by flat, SMA-positive cells, whereas the MyH-positive circular fibers were sometimes located adjacent to the SMA-positive fibers. However, in adults, smooth muscle tended to be clearly separated from striated muscle. The distribution of cells showing immunoreactivity for PGP9.5, S100 or c-kit did not differ between the oral and anal sides of the transition zone. Desmin was positive in the muscularis propria, but negative in the muscularis mucosae. Neither CD68-positive macrophages nor TUNEL-positive cells were present in the esophagus.

CONCLUSIONS

In the human esophagus, the smooth-to-striated muscle transition appears to stop at the mid-thoracic level. Cell death or transdifferentiation of smooth muscle appears unlikely, but phenotypic transformation into desmin-positive myofibroblasts is a possibility.

Fetal topohistology of the mesocolon transversum with special reference to fusion with other mesenteries and fasciae

The developing mesocolon transversum was investigated using hematoxylin and eosin-stained semiserial sections derived from 17 human fetuses between 12 and 30 weeks of gestation. The mesocolon was attached to the mesoduodenum and greater omentum until 12 weeks. However, the fetal duodenal attachment appeared not to correspond to the right colic flexure in adults. The greater omentum and mesocolon were likely to be irregularly folded at the attachment site possibly because the developing transverse colon "ran into" and pushed up the greater omentum and pancreatic head. Lymphatic vessels invaded the indistinct fusion plane to destroy the primary configuration. Moreover, the mesocolon seemed to "seize" or take-over some parts of the splenic side of the greater omentum, but the thick gastric side containing the right gastroepiploic artery and vein remained along the greater curvature. Until 20 weeks, the left colic flexure was fixed to the pancreatic tail, and near the flexure the mesocolon also fused with the renal fascia. The left splenic end of the greater omentum was folded and fused together to form a thick ligament-like structure, i.e., the gastrocolic ligament. In addition, near the duodenojejunal junction, a peritoneal bridge was often seen containing the inferior mesenteric artery or vein. Although surgeons generally believe that the mesocolon can be gently detached from the greater omentum, the fusion plane in adults appears to be the result of secondary modification and simplification by vascular development.

An investigation of the embryologic development of the fascia used as the basis for pancreaticoduodenal mobilization

BACKGROUND

The retropancreatic fusion fascia, or fascia of Treitz, is a critical anatomical landmark during retropancreatic mobilization of the pancreatic head and duodenum (the Kocher maneuver).

METHODS

Using semiserial sections from 24 human fetuses of 9-30 weeks gestation, we examined the development of this fascia.

RESULTS

Retroperitoneal fixation of the pancreas occurred at around 10 weeks. Up to 20 weeks, an apparent remnant of the mesoduodenum was attached to the now-distinct renal fascia. Lymphatic vessels and follicles congregated along the ventral aspect of the fusion plane during early development. In 20- to 30-week fetuses, the duodenum began to occupy a definite position and, at the same stage, a candidate for the fascia of Treitz was seen; it was separated from the thick renal fascia by loose connective tissue.

CONCLUSIONS

We hypothesize that mechanical stress during the development and growth of the duodenum causes the transformation of an indistinct remnant of the peritoneum into a distinct fascia. This mechanism is similar to that seen during the development of the renal fascia, in which the developing adrenal cortex and migrating kidney generate stress on a bundle of thin collagen fibers. Therefore, the fascia of Treitz is unlikely to be a simple remnant of the peritoneum. The fascia, if evident during surgery, should be attached to the pancreatic parenchymal side.