Last-intercalated node and direct lymphatic drainage into the thoracic duct from the thoracoabdominal viscera

Effectiveness of lymphadenectomy along the thoracic duct for radical esophagectomy

BACKGROUND

There has been much debate on whether to perform TD resection in radical esophagectomy for esophageal cancer from the perspectives of metastatic rate, effect on postoperative hemodynamics, and other factors. The objective of this study was to determine whether TDLN dissection contributes to improved prognosis.

METHODS

This study involved 1211 patients who underwent D2/D3 dissection with TD resection for thoracic esophageal cancer between 1984 and 2020. The lymph nodes along the TD were defined as TDLNs and the remaining No. 112 nodes as non-TDLNs. The metastatic rate in TDLNs and non-TDLNs and their outcomes were compared with those of other thoracic lymph nodes. Correlation with the invasion depth of the main lesion was also analyzed (T0-2 545 patients, T3-4 666 patients).

RESULTS

The metastatic rates in TDLNs/non-TDLNs in all patients were 7.3%/7.5%, respectively, while those in T0-2 were 2.2%/3.9%, and those in T3-4 were 11.5%/10.6%, with both having higher rates in advanced cases. The efficacy index (EI) for lymphadenectomy in T3-4 was 2.94 for TDLNs and 3.44 for non-TDLNs, with no significant difference. The metastatic rate in TDLNs by tumor site was as follows: Ut/Mt/Lt = 1.1/2.4/2.4% (T0-2) and 7.7/14.5/8.4% (T3-4), being especially high (~ 15%) in patients with advanced cases in Mt region. The EI was comparable or higher for TDLNs compared with other group-2 (Mt/Lt) and group-3 (Ut) regional lymph nodes, regardless of site.

CONCLUSIONS

The significance of TD resection was low in T0-2 due to the low metastatic rate but became evident in cases with invasion depth of T3-4. TDLN resection was at least as effective as dissection of other group-2 or -3 lymph nodes, including No. 112 nodes.

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 role of the lymphatic system in rabbit models for cancer metastasis research: a perspective from comparative anatomy

The elucidation of the pathogenesis of human diseases requires increasingly relevant and rigorous animal models. Therefore, investigators must select an appropriate mammalian model. Mice and rats are indispensable in the understanding of the mechanisms of human diseases, but other non-rodent mammals are required in certain situations. The rabbit is one such species. The rabbit exhibits greater biological similarities to humans than the mouse or rat, and the rabbit VX2 allograft cancer model has been used in a broad range of oncological studies, such as stromal responses, metastatic behaviors and therapeutic effects. Cancer cells in this model proliferate in a host rabbit that maintains a natural immunity, which makes this model attractive and unique. However, these examples constitute only a small number of advantages of a rabbit model. Numerous reports suggest that the rabbit is an attractive cancer-bearing animal model for the study of cancer metastasis and the lymphatic system. I briefly review the relevant medical literature and compare the rabbit lymphatic system with mice, rats and humans.

Establishment of successively transplantable rabbit VX2 cancer cells that express enhanced green fluorescent protein

Morphological detection of cancer cells in the rabbit VX2 allograft transplantation model is often difficult in a certain region such as serosal cavity where reactive mesothelial cells mimic cancer cells and both cells share common markers such as cytokeratins. Therefore, tagging VX2 cells with a specific and sensitive marker that easily distinguishes them from other cells would be advantageous. Thus, we tried to establish a successively transplantable, enhanced green fluorescent protein (EGFP)-expressing VX2 model. Cancer cells obtained from a conventional VX2-bearing rabbit were cultured in vitro and transfected with an EGFP-encoding vector, and then successively transplanted in Healthy Japanese White rabbits (HJWRs) (n = 8). Besides, conventional VX2 cells were transplanted in other HJWRs (n = 8). Clinicopathological comparison analyses were performed between the two groups. The success rate of transplantation was 100% for both groups. The sensitivity and specificity of EGFP for immunohistochemical detection of VX2 cells were 84.3 and 100%, respectively. No significant differences in cancer cell morphology, tumor size (P = 0.742), Ki-67 labeling index (P = 0.878), or survival rate (P = 0.592) were observed between the two. VX2 cells can be genetically altered, visualized by EGFP, and successively transplanted without significant alteration of morphological and biological properties compared to those of the conventional model.

Anatomy and physiology of the thoracic lymphatic system

The thoracic lymphatic system is one of the most complex and poorly understood systems of the human body, and much is still to be learned, especially in lymphatic physiology. Knowledge of the normal anatomy of this system as well as of its variations is nevertheless important for thoracic surgeons investigating and treating patients with lung or esophageal neoplasms.

Does senescence affect lymph node number and morphology? A systematic review

BACKGROUND

Immunosenescence may contribute to an observed increase in infections and specific cancers in the elderly. Lymph nodes play a key role in the body's immune system. A systematic review was undertaken to investigate the effects of senescence on lymph node number and morphology.

METHODS

Electronic databases Ovid MEDLINE, Embase and Google Scholar were searched for relevant articles examining normal lymph node number and morphology with senescence. Data on lymph node number, gross anatomy and histo-architecture were collated and analysed.

RESULTS

A total of 20 articles (15 human and 5 animal studies) were eligible for inclusion; many were limited by poorly standardized methods and relatively small sample sizes. However, there is evidence to suggest both a decrease in lymph node number and histological lymph node degeneration with senescence, at least in some lymph node basins. Degenerative changes include loss of lymphoid tissue from both the cortex and the medulla of lymph nodes, a reduction in the number and size of germinal centres, and changes such as hyalinization, fibrosis, fat deposition, a decrease in high endothelial venules and 'transparency'.

CONCLUSION

In this first systematic review to examine changes in lymph nodes with senescence, evidence was accrued to suggest a decline in lymph node number and morphological degeneration in older age groups. These changes might adversely affect immune function and the prognosis of infections and selected cancers in the elderly. Further research is required to confirm these morphological changes and to explore their potential immunological and functional effects.

Overt bone metastasis and bone marrow micrometastasis of early gastric cancer

Recently we encountered two cases of early gastric cancer (EGC) with bone metastasis after surgery. As they were not accompanied by overt liver, lung, or peritoneal metastasis, we examined the clinical significance of bone metastasis in EGC and its mechanisms by a review of the literature. We found only 10 cases of EGC complicated with overt bone metastasis in the English literature, so we also examined the Japanese reports of such cases. The main histologic type of cases of bone metastasis from EGC was the diffuse type, and there were long intervals between surgery and overt bone metastasis. One reason for such long intervals may have been the tumor dormancy. Two types of dormancy, dynamic and static, and two types of postoperative overt metastases, that of micrometastatic origin (normograde metastatic process) and that of bone marrow origin (retrograde metastatic process), were considered. We speculated that there may be specific routes by which the cancer cells infiltrate the bone marrow directly from EGC or lymph node metastasis. The procedures for diagnosing bone micrometastasis using monoclonal antibodies have recently been improved, but their accuracy rates are still not universally accepted. New, more reliable examinations are required to improve the survival rates of EGC.

Status of involved lymph nodes and direction of metastatic lymphatic flow between submucosal and t2-4 thoracic squamous cell esophageal cancers

BACKGROUND

Three-field lymph node dissection for thoracic esophageal cancer is associated with high morbidity and reduced quality of life after surgery. Consequently, minimized lymphadenectomy would be desirable, if appropriate. In the present study, we retrospectively analyzed the status of involved nodes and the direction of metastatic lymphatic flow from tumors into involved nodes to determine whether submucosal squamous cell esophageal cancers are potential candidates for minimized lymphadenectomy.

METHODS

We enrolled 199 patients who received esophagectomy with extensive lymph node dissection between 1989 and 2005 and retrospectively analyzed their prognoses, distribution of solitary metastatic lymph nodes, and the direction of metastatic lymphatic flow from the tumor, taking into consideration tumor location and depth.

RESULTS

Of these patients with submucosal cancers, 83% had 1 or 2 involved nodes, and their esophageal cancer-specific 5-year survival rate was 66%. Solitary lymph node metastasis did not occur in neck lymph nodes in lower thoracic submucosal esophageal cancers, and the direction of metastatic lymphatic flow from the tumor was almost always in one direction. By contrast, T2-4 cancers with 2-4 involved nodes had bidirectional metastatic lymphatic flow from the tumor.

CONCLUSIONS

There was a difference in the status of lymph node metastasis and the direction of metastatic lymphatic flow from tumors into involved nodes between submucosal and T2-4 thoracic squamous cell esophageal cancers. This analysis may be useful for developing an approach to minimized lymphadenectomy for thoracic esophageal cancers.

Preoperative mapping of lymphatic drainage from the tumor using ferumoxide-enhanced magnetic resonance imaging in clinical submucosal thoracic squamous cell esophageal cancer

BACKGROUND

In thoracic esophageal cancer, lymph node metastases distribute widely from the neck to the abdominal area as a result of a complex periesophageal lymphatic network. The aim of the present study was to evaluate the potential clinical utility of a new method of mapping lymphatic drainage from tumors using ferumoxide-enhanced magnetic resonance imaging (MRI).

METHODS

Twenty-three patients with clinical submucosal thoracic squamous cell esophageal cancer were examined. Ferumoxides were injected endoscopically into the peritumoral submucosal layer, after which their appearance in the lymph nodes in the neck, superior mediastinum, and abdomen was evaluated using MRI.

RESULTS

Flux of ferumoxides from tumors was detected in all 23 patients. Among the 20 patients with middle and lower thoracic esophageal cancers, there was no lymphatic drainage to the neck in 5 (25%) patients, none to the neck and superior mediastinum in 4 (20%), and none to the abdomen in 2 (10%), which could enable the extent of lymph node dissection to be reduced. We diagnosed clinical negative lymph node metastasis (N0) in 17 patients; the remaining 6 patients were diagnosed with clinical lymph node metastasis. Two patients (12%) diagnosed clinical N0, showed pathologic lymph node metastasis. Ferumoxide-enhanced MRI detected an influx of contrast agent into the metastatic node in both patients.

CONCLUSIONS

Ferumoxide-enhanced MRI lymphatic mapping enables detection of the direction and area of lymphatic flux. It thus has the potential to improve our ability to gauge the appropriate extent of treatment in clinical submucosal squamous cell esophageal cancer.

Anatomy and histology of Virchow's node

A regional lymphatic system is composed of the first, second, third and even fourth or much more intercalated nodes along the lymptatic route from the periphery to the venous angle or the thoracic duct. The third or fourth node is usually termed the last-intercalated node or end node along the route. Similarly, one of the supraclavicular nodes is known to correspond to the end node along the thoracic duct. It is generally called 'Virchow's node', in which the famous 'Virchow's metastasis' of advanced gastric cancer occurs. The histology of this node has not been investigated, although region-specific differences in histology are evident in human lymph nodes. We found macroscopically the end node in five of 30 donated cadavers. Serial sections were prepared for these five nodes and sections stained with hematoxylin and eosin. Histological investigation revealed that, on the inferior or distal side of the end node, the thoracic duct divided into three to 10 collateral ducts and these ducts surrounded the node. The node communicated with the thoracic duct and its collaterals at multiple sites in two to three hilus-like portions, as well as along the subcapsular sinus. Thus, the end node was aligned parallel to the thoracic duct. Moreover, the superficial and deep cortex areas of the end node were fragmented to make an island-like arrangement, which may cause the short-cut intranodal shunt. Consequenly, the filtration function of most of Virchow's node seemed to be quite limited.

Anatomy of right recurrent nerve node: why does early metastasis of esophageal cancer occur in it?

Early, distant and/or skip metastasis of squamous-cell thoracic esophageal cancer frequently occurs in the right recurrent nerve node (recR). However, the specific lymphatic route without a nodal relay, such as the submucosal ascending route, was not known for the recR afferent. Using 20 donated cadavers, macroscopic, and histological observations were performed on the recR and its surrounding lymphatics, especially afferent routes from the esophagus to the recR. Most afferent vessels of the recR originated from the right paratracheal node. However, the recR often (12/20) received a major submucosal lymphatic drainage route ascending along the thoracic esophagus. The submucosal vessel came out of the esophagus and ran in a longitudinal connective tissue mass along the right tracheo-esophageal groove. A direct drainage route was often (13/20) seen from the recR to the venous system. Moreover, because of the specific histology, collaterals seemed to be present around the recR. In the regional nodes of the intrathoracic esophagus, the recR histology was characterized by the high proportion of lymphocyte accumulating areas or the cortex. From the midthoracic level, metastatic cancer cells seemed to reach the recR via esophageal submucosal vessels in the early stage. Large lymphocyte accumulating areas of the recR suggested higher filtration capacity than other distal nodes. However, the collateral of the recR and its direct drainage to the venous system suggested that the recR involvement often corresponds to a systemic disease.

A Second Malignancy Is the Major Cause of Death among Thoracic Squamous Cell Esophageal Cancer Patients Negative for Lymph Node Involvement

BACKGROUND

The aim of the present study was to determine the major causes of death among esophageal cancer patients whose lymph nodes did not show metastasis at the time they received esophagectomy, and to consider strategies for improving survival rates among these patients.

STUDY DESIGN

Between 1989 and 1999, 93 of our patients who underwent curative esophagectomy with extended lymph node dissection for thoracic squamous cell esophageal cancer showed no lymph node metastasis. We followed up these node-negative patients for as long as 10 years and determined the major causes of death.

RESULTS

Sixty-three patients were still alive after esophagectomy, although 30 had died. Six patients died within 3 years after esophagectomy as a direct result of recurrence of their esophageal cancer; 13 died as a result of a second (extraesophageal) malignancy. Within the first 3 years, the major causes of death were recurrence (35%) and the second malignancy (35%); thereafter, the major cause was only the second malignancy (54%). There was no difference in the survival rates among patients with earlier, synchronous, or subsequent malignancies. Univariate and multivariate analyses of the 10-year survival showed the independent prognostic factors to be recurrence of esophageal cancer and development of a second malignancy, which respectively increased the risk of death 6.4 and 2.7 times.

CONCLUSIONS

The major cause of reduced survival among thoracic squamous esophageal cancer patients, whose lymph nodes did not show metastasis, was a second malignancy. New strategies aimed at preventing or treating synchronous and subsequent malignancies could prolong the survival of these patients.

Comparative histology of lymph nodes from aged animals and humans with special reference to the proportional areas of the nodal cortex and sinus

Lymph nodes are composed of a lymphocyte-rich area or cortex (subdivided into the superficial and deep cortex and the medullary cord) and another, macrophage-rich area (incorporating the subcapsular and medullary sinuses). We measured the proportional area of the cortex in lymph nodes from aged experimental mammals (rats, guinea pigs, dogs and rabbits) and elderly Japanese humans. The cervical, axillary and inguinal nodes were generally richer in cortex tissue than the pulmonary regional and mesenteric nodes. Histological heterogeneity and medullary sinus dominance were much more evident in the human nodes than in those from animals, except for the guinea pig thoracic node. Human pulmonary regional nodes were characterized by a large medullary sinus; in guinea pigs, these nodes had a similar histology but the T lymphocyte-containing areas were smaller and thinner than in humans. The paraaortic node was well developed in humans and dogs, but not in other animals tested. These species- and region-specific histological differences may influence the evaluation of experimental animal models of lymph node function, such as those recently identified for research into sentinel nodes.

Superior mediastinal and neck lymphatic mapping in mid- and lower-thoracic esophageal cancer as defined by ferumoxides-enhanced magnetic resonance imaging

OBJECTIVE

The purpose of this study was to detect lymphatic drainage into the superior mediastinum and neck in thoracic esophageal cancer patients using ferumoxides-enhanced magnetic resonance imaging (MRI), and to have this information assist in determining the appropriate extent of lymphadenectomy.

METHODS

Nine male patients with T2-T3 mid- and lower-thoracic esophageal cancer with lymph node metastasis were examined. The day before surgery, ferumoxides was endoscopically injected into the submucosal layer of the peritumoral lesion. Thereafter, lymph nodes in the superior mediastinum and neck, which were shown to be ferumoxides-enhanced on MRI, were harvested and evaluated; magnetic force from all harvested lymph nodes was measured ex vivo.

RESULTS

MRI of the superior mediastinum and neck revealed 1(median) ferumoxides-enhanced lymph nodes in eight (89%) patients, and there was laterality in the lymphatic mapping in both areas. Of the 15 lymph nodes into which drainage was detected by enhanced MRI, 12 (80%) were magnetite-positive. In six patients (67%), magnetic resonance enhanced lymph nodes corresponded completely with the ex vivo magnetite examination, and in 3 patients (33%) there was partial agreement. In 3 (60%) of the 5 patients that showed paratracheal and/or supraclavicular lymph node metastases, all of the affected nodes were detected by MRI; in one patient some of the affected nodes were detected.

CONCLUSION

Ferumoxides-enhanced MRI is useful for visualizing lymphatic drainage to the superior mediastinum and neck in thoracic esophageal cancer. It is an adequate procedure to form an estimate on the appropriate extent of lymphadenectomy.

Histologic heterogeneity and intranodal shunt flow in lymph nodes from elderly subjects: a cadaveric study

Gaps of the superficial cortex of the lymph node provide intranodal shunts that are more often the cause of skip metastasis than are collateral vessels. Examination of lymph nodes from cadavers of elderly subjects often revealed cortical gaps, especially in specific three-dimensional assembled cords; these cortical gaps were readily seen in para-aortic and pelvic nodes. This architecture seemed to be more appropriate for a systemic immune response than a local defense. Evidence of poorly developed cortices, anthracosis, and hyalinization also suggested impaired nodal function. We suspect that this histologic heterogeneity, perhaps a result of aging, affects the nodal trapping of colorimetric/isotopic tracers and metastatic cancer cells. This may have implications for lymphatic mapping of the sentinel lymph node in elderly patients with early-stage cancer.

Gaps and fragmentation of the superficial cortex in the abdominal and pelvic lymph nodes of elderly Japanese

Gaps and fragmentation of the superficial lymph node cortex are considered to provide intranodal shunt flow between the afferent and efferent vessels. Using serial sections of 205 nodes obtained from 27 donated cadavers more than 70 years of age, we examined the histological architecture of the abdominal and pelvic nodes in elderly Japanese. Secondary follicles were rare in the specimens. Cortex gaps were, to a greater or lesser degree, found in all nodes. We classified these nodes into three types according to how often the gap occurred. Type 1 nodes, with a relatively complete shield for the afferent lymph, were most frequently found in gastric nodes, whereas type 3 nodes, with numerous gaps, were often observed in the colic, para-aortic and pelvic nodes. The type 3 nodes showed a specific architecture characterized by a fragmented superficial cortex, three-dimensionally assembled cords and a common sinus between them. Primary follicles were located in the assembled cord structures as well as at the superficial cortex. Irrespective of the type, B and T lymphocyte areas were intermingled in the cortex-like areas. The present results reveal region-specific histological heterogeneity in aged human visceral nodes. Due to increased surface areas, the type 3 architecture seemed to accelerate systemic immunity rather than act as a local barrier in the para-aortic and pelvic nodes, which are located centrally along the lymphatic drainage routes. However, thick trabeculae often seemed to develop in the type 3 sinus to decrease nodal function with aging.

Submucosal territory of the direct lymphatic drainage system to the thoracic duct in the human esophagus

OBJECTIVE

To investigate how large submucosal drainage territory extends in lymphatic drainage vessels of the esophagus with and without nodal delay and which morphologies are shown when passing through the muscularis propria.

METHODS

Submucosal territories of the 22 highly selected direct drainage vessels of 17 esophagi were histologically examined using transverse or sagittal serial sections. Afferent vessels from the esophagus to the subcarinal (6 esophagi) and para-esophageal (5 esophagi) nodes were also examined to identify their courses and drainage territories.

RESULTS

We found the direct drainage vessel from the esophagus in 17 of 75 cadavers macroscopically (22.7%). A single submucosal drainage unit gave off 1-3 thick drainage vessels passing through a complete muscle gap of the 2 muscular layers. The unit extended longitudinally for >40 mm but was restricted to the right and/or dorsal quadrants of the esophagus. In contrast, drainage routes with a nodal relay originated from the intermuscular area, except 1 case when the adjacent or concomitant esophageal artery and vein provided the complete muscle gap.

CONCLUSIONS

Due to the extended longitudinal but restricted transverse territory of the direct drainage system without a nodal relay and because of the suggested much more frequent occurrence in patients than in cadavers, when superficial carcinoma is found in the dorsal and/or right quadrants of the esophagus, we recommend detailed presurgical investigations of cervical nodes. In contrast, afferents from the esophagus to the first regional node usually seemed to be less responsible for early nodal metastasis than the direct drainage route because of their intermuscular origins.

Afferent and efferent lymph-collecting vessels of the submandibular nodes with special reference to the lymphatic route passing through the mylohyoid muscle

BACKGROUND

Although metastasis of cancer in the oral region to the submandibular node is well described, there has been no anatomic representation of lymph vessels penetrating the oral floor and draining into the node.

MATERIALS AND METHODS

Ninety specimens were obtained from formalin-fixed, donated cadavers. Histologic observations using serial sections followed the macroscopic observations.

RESULTS

In 19 of 90 specimens, we found afferent collecting lymph vessels exiting from the mylohyoid surface and draining into the preglandular submandibular node. In 3 of the 19 specimens, collecting vessels passing through the narrow muscle gap with or without arteries, veins, and nerves were identified histologically. The postglandular submandibular node was not evident in the drainage route.

CONCLUSIONS

Although it carries a low incidence, because of the direct lymphatic route or pathway between the oral region and preglandular submandibular node, the pathologically positive supraomohyoid node sometimes seems to be found even in elective neck dissection. However, we speculate that sentinel node investigation would reveal the much more critical role of the jugulodigastric node not only as the actual sentinel node but also as the common terminal node along the various drainage routes from the oral region.