Lymphangiogenesis and expression of specific molecules as lymphatic endothelial cell markers

In recent years, several functional molecules specifically expressed and localized in lymphatic endothelial cells, such as 5'-nucleotidase, lymphatic vessel endothelial receptor-1, vascular endothelial growth factor receptor-3, podoplanin and Prox-1, have been identified. The discovery of the lymphatic endothelial cell markers facilitated detailed analysis of the nature and structural organization of the lymphatic vessels and their growth (lymphangiogenesis). As a result, over the past few years, advances have been made in understanding the cellular and molecular aspects of physiological lymphangiogenesis and tumor-induced lymphangiogenesis. The biology of lymphangiogenesis, particularly the mechanism of its regulation, is very important in understanding the formation of the lymphatic system as a biological regulation system transporting tissue fluid and wandering cells, including lymphocytes, and disease involving lymphangiogenesis. The understanding of the molecular mechanism of lymphangiogenesis and the elucidation of the development of normal and pathological tissues are expected to lead to the development of therapy for intractable diseases, such as malignant tumors and lymphedema.     

Interleukin-6 signalling regulates vascular endothelial growth factor-C synthesis and lymphangiogenesis in human oral squamous cell carcinoma

Lymph node metastasis is associated with resistance to conventional therapy and poor survival of patients with oral squamous cell carcinoma (OSCC). Although lymphangiogenesis is well known to be associated with the occurrence of lymph node metastasis in various cancers, the precise mechanisms of lymphangiogenesis in OSCC are largely unknown. IL-6, a potent pro-inflammatory cytokine, has been shown to play active roles in various cancers, including OSCC. This study aimed to investigate the involvement of IL-6 signalling in lymphatic metastasis and to evaluate the efficacy of tocilizumab, a humanized anti-human IL-6 receptor antibody, as an anti-lymphangiogenic agent for OSCC. This investigation confirmed that levels of expression of IL-6 protein and VEGF-C mRNA in OSCC tissues were significantly correlated with lymph node metastasis in patients with OSCC, as assessed by immunohistochemical analysis and real-time quantitative RT-PCR. In vitro studies showed that IL-6 regulated VEGF-C mRNA expression in a human OSCC cell line, SAS cells, through the phosphoinositide 3-kinase-Akt pathway. In addition, treatment with tocilizumab led to markedly reduced VEGF-C mRNA expression and OSCC-related lymphangiogenesis in SAS xenografts. Together, these data suggest that tocilizumab acted as expected: it inhibited lymph node metastasis in OSCC by reducing tumour lymphangiogenesis.     

Inducible nitric oxide synthase activity correlates with lymphangiogenesis and vascular endothelial growth factor-C expression in head and neck squamous cell carcinoma

Nitric oxide (NO) is a diatomic free radical molecule that has been implicated in tumour angiogenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the mechanism underlying the effect of NO on tumour spread remains largely unknown. Tumour lymphangiogenesis has recently received considerable attention and there is increasing evidence that it is relevant for metastasis to lymph nodes in HNSCC. Here, we study the correlation between inducible NOS synthase (iNOS) activity and lymphangiogenesis in a series of 60 HNSCCs and the possible involvement of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C. HNSCC presenting with lymph node metastasis had a significantly higher lymphatic vessel density in both the tumour mass and the peritumour area (p = 0.006 and p = 0.001, respectively). Similarly, tumours with lymph node metastasis showed greater lymphatic vessel area than tumours with no lymph node involvement (p = 0.001 for intratumour lymphatics and p < 0.001 for peritumour lymphatics). iNOS activity measured in specimens from the tumour periphery correlated strongly with both lymphatic vessel density and lymphatic vessel area (p = 0.01, rs = 0.45 and p < 0.001, rs = 0.725, respectively). Conversely, these correlations were not observed in specimens from the tumour core. In addition, VEGF-C mRNA expression was significantly elevated in tumours with high iNOS activity (p = 0.008, rs = 0.563), and VEGF-C expression correlated positively with the presence of lymph node metastases (p = 0.03). In vitro, in the A431 human squamous carcinoma cell line, exogenous and endogenous stimulation of the iNOS pathway led to up-regulation of VEGF-C, which was blocked by the NOS inhibitor L-NNA. Taken together, our results indicate that iNOS activity may promote lymphangiogenesis and spread to lymph nodes in HNSCC, with the possible involvement of VEGF-C.     

Mechanisms of lymphatic metastasis in human colorectal adenocarcinoma

The invasion of lymphatic vessels by colorectal cancer (CRC) and its subsequent spread to draining lymph nodes is a key determinant of prognosis in this common and frequently fatal malignancy. Although tumoural lymphangiogenesis is assumed to contribute to this process, review of the current literature fails to support any notion of a simple correlation between lymphatic vessel density and CRC metastasis. Furthermore, attempts to correlate the expression of various lymphangiogenic growth factors, most notably VEGF‐C and VEGF‐D, with the lymphatic metastasis of CRC have provided contradictory results. Recent evidence from animal and human models of tumour metastasis suggests that complex functional and biochemical interactions between the microvasculature of tumours and other cell types within the tumour microenvironment may play a pivotal role in the behaviour of commonly metastasizing tumours. Indeed, previous insights into tumoural blood vessels have provided candidate markers of tumoural angiogenesis that are currently the subject of intense investigation as future therapeutic targets. In this review article we survey the current evidence relating lymphangiogenesis and lymphangiogenic growth factor production to metastasis by CRC, and attempt to provide some insight into the apparent discrepancies within the literature. In particular, we also discuss some new and provocative insights into the properties of tumoural lymphatics suggesting that they have specific expression profiles distinct from those of normal lymphatic vessels and that appear to promote metastasis. These findings raise the exciting prospect of future biomarkers of lymphatic metastasis and identify potential targets for new generation anti‐tumour therapies. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Follicular dendritic cell sarcoma of the colon mimicking stromal tumour

AIMS: Follicular dendritic cell tumours are very rare neoplasms that often occur in lymph nodes. We report here a case in the colon, a hitherto unreported site, in a 37-year-old female. The differentiation from gastrointestinal stromal tumour is emphasized. METHODS and RESULTS: The tumour was tan, elastic and solid with surface ulceration. Microscopically, it was composed of oval to spindle tumour cells with syncytial cytoplasm arranged in fascicular and whorled patterns. There were many infiltrating lymphocytes. The histological appearance resembled gastrointestinal stromal tumour, thymoma or meningioma. Distinct from the stromal tumour, the lymph node was also involved by the tumour. Immunohistochemically, the tumour cells were positive for CD21, CD35 and CD68, but negative for cytokeratin, CD34, smooth muscle actin, desmin, S100 protein, epithelial membrane antigen, leukocyte common antigen, HMB-45 and c-kit. In-situ hybridization study was negative for Epstein-Barr virus RNA sequences. Ultrastructurally, the tumour cells possessed cytoplasmic processes joined by desmosomes. CONCLUSIONS: This entity should be considered in the list of differential diagnoses for gastrointestinal stromal tumour. The lymph node metastasis and immunohistochemical features are of value for identification of this rare neoplasm.     

Induction of contact-dependent endothelial apoptosis by osteosarcoma cells suggests a role for endothelial cell apoptosis in blood-borne metastasis

Although tumour cells are believed to migrate between endothelial cells early in metastasis, the possibility remains that endothelial apoptosis may also contribute to the tumour's breach of the vascular barrier. Although seemingly inconsistent with tumour angiogenesis, one publication describes the induction of contact-dependent apoptosis in cultured endothelium by tumour cells. The cell culture data are, however, open to challenge on technical grounds while there are no confirmatory reports. The present paper describes experiments overcoming these limitations. SAOS-2 human osteosarcoma cells and two rat carcinoma cell lines were co-cultured with human umbilical vein endothelial cells (HUVECs) and cultures labelled by surface lectin histochemistry for endothelium. The HUVEC culture density was determined and SAOS-2 cells, but not rat carcinoma cells, were found significantly to reduce HUVEC survival despite the release of potent growth factors as determined in separate experiments with tumour cell conditioned medium. Lectin labelling combined with light microscopy, transmission electron microscopy, flow cytometry for both lectin binding and DNA content, and DNA gel electrophoresis of SAOS-2/HUVEC co-cultures revealed extensive HUVEC apoptosis. These findings indicate contact-dependent endothelial apoptosis by SAOS-2, while this activity appeared weaker and overwhelmed by HUVEC proliferation with rat carcinoma cells. Importantly, this study supports the suggestion that endothelial apoptosis may be important for metastasis and suggests a complex interplay between endothelial proliferation and apoptosis in tumours.     

Tumour necrosis factor superfamily member 15 (Tnfsf15) facilitates lymphangiogenesis via up‐regulation of Vegfr3 gene expression in lymphatic endothelial cells

Lymphangiogenesis is essential in embryonic development but is rare in adults. It occurs, however, in many disease conditions including cancers. Vascular endothelial growth factor‐C/D (VEGF‐C/D) and VEGF receptor‐3 (Vegfr3) play a critical role in the regulation of lymphangiogenesis. We investigated how the VEGF‐C/Vegfr3 signalling system is regulated by tumour necrosis factor superfamily member 15 (Tnfsf15), an endothelium‐derived cytokine. We report here that Tnfsf15, which is known to induce apoptosis in vascular endothelial cells, can promote lymphatic endothelial cell (LEC) growth and migration, stimulate lymphangiogenesis, and facilitate lymphatic circulation. Treatment of mouse LECs with Tnfsf15 results in up‐regulation of Vegfr3 expression; this can be inhibited by gene silencing of death domain‐containing receptor‐3 (DR3; Tnfrsf25), a cell surface receptor for Tnfsf15, with siRNA, or by blocking Tnfsf15–DR3 interaction with a Tnfsf15 neutralizing antibody, 4‐3H. Additionally, Tnfsf15/DR3 signalling pathways in LECs include activation of NF‐κB. Tnfsf15‐overexpressing transgenic mice exhibit a marked enhancement of lymph drainage; this is confirmed by treatment of wild‐type mice with intraperitoneal injection of recombinant Tnfsf15. Moreover, systemic treatment of pregnant Tnfsf15 transgenic mice with 4‐3H leads to inhibition of embryonic lymphangiogenesis. Our data indicate that Tnfsf15, a cytokine produced largely by endothelial cells, facilitates lymphangiogenesis by up‐regulating Vegfr3 gene expression in LECs, contributing to the maintenance of the homeostasis of the circulatory system. This finding also suggests that Tnfsf15 may be of potential value as a therapeutic tool for the treatment of lymphoedema. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Histopathological study of lymphatic invasion in squamous cell carcinoma (O-1N) with high potential of lymph node metastasis

The process of lymph node metastasis was studied in an animal model (termed O-1N) that was successfully established using a metastatic tumor to the submandibular lymph node from a chemically induced squamous cell carcinoma of the hamster tongue. The model has been maintained by serial transplantation of metastatic tumors into the buccal pouch. Lymphovascular invasion of transplanted O-1N in the tongue was examined in serial histologic sections. Lymphatic vessels were distinguished from blood vessels by Masson's trichrome stain for vascular smooth muscle, BSA-I lectin binding for vascular endothelium, and laminin and type IV collagen immunostaining for the vascular basement membrane. Transplanted tumors enlarged progressively with invasion of surrounding tissues of the tongue and resulted in lymph node metastasis in all animals with successful takes. Local growth of the tumors in the tongue was accompanied by stromal proliferation with abundant dilated lymphatic vessels which contained clusters of tumor cells. On serial sections, the carcinoma cell clusters in lymphatics in the close proximity of tumor nests were in continuity with adjacent tumor nests, whereas such continuity was not recognized in those occurring apart from tumor nests. The formation of isolated carcinoma cell clusters resulting from disintegration of elongated processes of tumor nests with invasion of lymphatics and subsequent transport in lymphatics and deposition in lymph nodes in clusters were well demonstrated in other serial sections. The key step of lymph node metastasis therefore appears to be direct invasion of lymphatic vessels by tumor cells, similar to their invasion of adjacent tissues but different from the way that blood cells escape through vessel walls. Proliferation of lymphatics around tumor nests and transport of tumor cells in clusters would also contribute to the production of metastatic deposits in lymph nodes.     

VEGF-C表达与胰腺癌淋巴结转移及预后的关系

目的 观察血管内皮生长因子(VEGF)-C在胰腺癌组织内的表达情况,分析VEGF-C的表达与胰腺癌淋巴结转移和预后之间的关系。方法 取胰腺癌病例52例,其中,伴淋巴结转移组36例,无淋巴结转移组16例。应用免疫组化法和Western blot技术观察VEGF-C在胰腺癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,观察胰腺癌组织内淋巴管生成的情况。采用Kaplan-Meier法绘制生存曲线判断VEGF-C的表达对胰腺癌预后的影响。结果 Western blot和免疫组化法检测结果表明,VEGF-C主要表达于胰腺癌细胞浆内,淋巴结转移组阳性表达量明显高于无淋巴结转移组(p<0.05)。D2-40表达于胰腺癌组织内淋巴管内皮细胞,VEGF-C阳性组淋巴管数密度明显高于VEGF-C阴性组(p<0.05),表明VEGF-C的表达与胰腺癌淋巴管生成密切相关。Kaplan-Meier生存分析表明VEGF-C表达阴性患者的生存率均高于VEGF-C表达阳性患者,VEGF-C的表达影响患者的预后。结论 VEGF-C在胰腺癌的淋巴管生成和淋巴结转移过程中发挥重要作用,VEGF-C的表达是影响胰腺癌患者预后的主要因素之一。     

VEGF-C在淋巴管生成及乳腺癌淋巴道转移中的作用

目的： 探讨阻断VEGF-C/Flt-4调控系统对淋巴管生成和乳腺癌淋巴道转移的影响。方法： 体外培养胎牛胸导管内皮细胞，观察VEGF-C和抗Flt-4抗体对淋巴管内皮细胞增殖的影响；设计合成VEGF-C反义脱氧寡核苷酸（ASODN），体外实验观察其对VEGF-C基因表达的影响；建立乳腺癌裸鼠原位移植瘤模型并观察ASODN对肿瘤淋巴管生成及肿瘤生长转移的影响。结果： 加入前列腺癌细胞PC3(高表达VEGF-C)上清后，淋巴管内皮细胞增殖活跃；加入抗Flt-4抗体后各时段细胞计数均明显少于其它各组。体外实验RT-PCR及 Western blotting显示ASODN作用的MCF-7细胞组VEGF-C mRNA及蛋白表达均低于对照组。体内RT-PCR检测表明ASODN组移植瘤VEGF-C mRNA表达明显受抑制；5-Nase-ALPase双重酶组织化学法结果显示ASODN组移植瘤的淋巴管生成明显减少；ASODN组肿瘤生长速度较对照组缓慢，且肿瘤体积、淋巴结转移明显低于对照组。结论： VEGF-C/Flt-4调控系统与乳腺癌组织的淋巴管生成及肿瘤的淋巴道转移密切相关。阻断淋巴管内皮细胞Flt-4表达，可在一定程度上抑制肿瘤细胞诱导的淋巴管内皮细胞增殖；ASODN通过下调乳腺癌VEGF-C的表达，减少肿瘤淋巴管的生成及淋巴结转移。     

Tumor‐associated lymphatic endothelial cell promotes invasion of cervical cancer cells

The most common way for cervical cancer to spread is through the lymphatic system. Tumor‐associated lymphatic endothelial cell (TLEC) has been considered to play a crucial role in metastasis of certain cancers. The aim of this study was to isolate TLEC from human cervical cancers and explore its involvement in metastasis‐associated behaviors in vitro. Lymphatic vessels in 62 cervix tissue specimens ranging from cervical intraepithelial neoplasia (CIN) to advanced invasive cancer were detected using immunochemical staining with D2‐40 antibody. Relation of lymphatic vessel density (LVD) to clinicopathological characters was analyzed. Primary TLECs were isolated by LYVE‐1 immuno‐magnetic beads from cervical cancer tissues and verified through expression of LEC markers Prox‐1 and D2‐40, and then cultured in vitro. Invasiveness and viability of cells were assessed by transwell assay and typan blue exclusion, respectively. Our results showed that higher LVD was significantly associated with advanced FIGO stage, pelvic lymphatic nodal metastasis (LNM), and poorer cell differentiation. TLECs were successfully primarily isolated and cultured in vitro. Supernatant of TLEC enhanced invasiveness of Hela cell, but did not significantly affect cell viability. In conclusion, TLECs might actively promote lymphatic metastasis of cervical cancer. Further studies are needed to demonstrate the underlying mechanisms.     

VEGF-A和C在人结肠癌淋巴管生成和淋巴道转移中的作用

目的分析血管内皮生长因子(VEGF)-A和VEGF-C在人结肠癌组织的表达及与结肠癌淋巴管生成和淋巴道转移的关系。方法取人结肠癌组织91例,应用免疫组化方法检测VEGF-A和VEGF-C在结肠癌组织中的表达。应用D2-40标记结肠癌组织的淋巴管,观察结肠癌组织的淋巴管生成情况。结果结肠癌组织中VEGF-A和VEGF-C的表达水平明显高于正常组织,VEGF-A和VEGF-C表达阳性的结肠癌组织的淋巴管密度(LVD)明显高于阴性组织,VEGF-A和VEGF-C的表达及LVD均与淋巴结转移及Duke's分期相关。结论结肠癌组织VEGF-A和VEGF-C过表达与结肠癌的淋巴管生成和淋巴道转移相关。     

The stable prostacyclin analogue Cicaprost inhibits metastasis to lungs and lymph nodes in the 13762NF MTLn3 rat mammary carcinoma

Prostacyclin and its stable analogues have been shown to interfere specifically with certain steps of the metastatic cascade. The antimetastatic activity of the stable prostacyclin analogue Cicaprost (Schering AG) on haematogenous metastasis in a series of tumours in rats and mice has been well established. In order to test the effect of Cicaprost on lymphogenous metastasis we chose the metastatic cell clone MTLn3 derived from the 13762NF rat mammary carcinoma. The effect of Cicaprost on prevention of lung metastasis, lymph node metastasis and primary tumour growth was investigated. Cicaprost given in daily doses of 0.01, 0.03 and 0.1 mg/kg orally, reduced the number of lung metastases in a dose-dependent manner. Whereas the median number of lung metastases in the controls was greater than 1000, Cicaprost at a dose of 0.1 mg/kg reduced the number of lung metastases to between 11 and 100. The weight of the ipsilateral axillary lymph nodes was diminished by Cicaprost to 30–50% of controls. Moreover, metastasis to the contralateral axillary lymph node was completely inhibited by Cicaprost at all three doses tested. Cicaprost did not influence the growth rate of the MTLn3 cell clone implanted into the mammary fat pad or the weight of the primary tumour at the end of treatment. In conclusion, in addition to its dose-dependent effect on haematogenous metastasis, Cicaprost strongly inhibits lymph node metastasis.     

Intratumoral lymphangiogenesis of esophageal squamous cell carcinoma and relationship with regulatory factors and prognosis

The clinical and pathological significance of intratumoral lymphangiogenesis (ITL) with human esophageal squamous cell carcinomas (ESCC) remains unclear, as does the role of signaling molecules such as vascular endothelial growth factor (VEGF)-A,C, platelet-derived growth factor (PDGF)-A, and p53, in the regulation of ITL. Lymphatic vessel density (LVD) was significantly increased in VEGF-A and VEGF-C immunohistochemical score 1 and 2-3 groups as compared to the score 0 group and also with high of VEGF-A, VEGF-C and PDGF-A mRNA expression. Both LVD and blood vessel density (BVD) were significantly greater in the p53 gene mutant group than in the wild-type group. Lymph node metastasis was significantly more frequent with than without ITL and Kaplan-Meier analysis indicated a significantly poorer prognosis. Multivariate analysis using Cox proportional hazard method showed that invasion depth, lymph node metastasis and ITL were independent prognostic factors.     

乳腺癌中Syk、VEGF-C表达与淋巴结转移的关系

目的研究乳腺癌组织中Syk、VEGF-C的表达与淋巴结转移的关系。方法分别采用免疫组织化学EnVision两步法及SP法检测55例乳腺癌组织中Syk、NFκB(p65)及VEGF-C的表达情况。结果55例乳腺癌组织中,Syk、VEGF-C及p65阳性率分别为50.9%,56.4%,81.8%。Syk在淋巴结转移组的表达低于无淋巴结转移组(P0.05);VEGF-C在淋巴结转移组的表达高于无淋巴结转移组(P0.05);p65在两组之间的表达差异无显著性(P0.75),p65胞核移位率在淋巴结转移组高于无淋巴结转移组(P0.025)。随着Syk表达增强VEGF-C的表达减弱,二者呈负相关(r=-0.620,P=0.000);p65胞核移位与Syk的表达强度降低有关(r=0.448,P=0.002),而与VEGF-C的表达强度增高有关(r=0.310,P=0.036)。结论乳腺癌中,Syk可能通过抑制NFκB的活性而下调VEGF-C的表达,从而抑制乳腺癌的淋巴结转移。     

人endostatin体外诱导血管内皮细胞凋亡的实验研究

目的 探讨人endostatin抑制血管内皮细胞增殖的作用机制。方法 在含重组人endostatin蛋白和10%小牛血清的DMEM培养基中，培养人脐静脉内皮细胞ECV304。72h后，采用透射电镜，流式细胞术细胞周期分析和细胞核DNA的1.5%琼脂糖凝胶电泳，检测重组人endostatin蛋白作用后，血管内皮细胞的凋亡。结果 透射电镜下可见实验组ECV304细胞核染色质浓缩，边集，核碎裂及胞浆浓缩等，呈典型的凋亡细胞的形态学表现，流式细胞术细胞周期分析显示，在G1期峰前存在1个凋亡峰（20.6%)，1.5%琼脂糖凝胶电泳显示，细胞核DNA呈梯状，对照组ECV304细胞表达正常。结论 重组人endostatin蛋白可诱导血管内皮细胞凋亡，是其抑制血管内皮细胞增殖的原因之一。     

Circulating tumour tissue fragments in patients with pulmonary metastasis of clear cell renal cell carcinoma

Tumour metastasis is the result of a complex sequence of events, including migration of tumour cells through stroma, proteolytic degradation of stromal and vessel wall elements, intravasation, transport through the circulation, extravasation and outgrowth at compatible sites in the body (the ‘seed and soil’ hypothesis). However, the high incidence of metastasis from various tumour types in liver and lung may be explained by a stochastic process as well, based on the anatomical relationship of the primary tumour with the circulation and mechanical entrapment of metastatic tumour cells in capillary beds. We previously reported that constitutive VEGF‐A expression in tumour xenografts facilitates this type of metastatic seeding by promoting shedding of multicellular tumour tissue fragments, surrounded by vessel wall elements, into the circulation. After transport through the vena cava, such fragments may be trapped in pulmonary arteries, allowing them to expand to symptomatic lesions. Here we tested whether this process has clinical relevance for clear cell renal cell carcinoma (ccRCC), a prototype tumour in the sense of high constitutive VEGF‐A expression. To this end we collected and analysed outflow samples from the renal vein, directly after tumour nephrectomy, in 42 patients diagnosed with ccRCC. Tumour fragments in venous outflow were observed in 33% of ccRCC patients and correlated with the synchronous presence or metachronous development of pulmonary metastases (p < 0.001, Fisher's exact test). In patients with tumours that, in retrospect, were not of the VEGF‐A‐expressing clear cell type, tumour fragments were never observed in the renal outflow. These data suggest that, in ccRCC, a VEGF‐A‐induced phenotype promotes a release of tumour cell clusters into the circulation that may contribute to pulmonary metastasis. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Tenascin-C expression in Merkel cell carcinoma lymph node metastasis

Expression of tenascin-C (Tn-C) has been shown to correlate with invasion and metastasis in Merkel cell carcinoma (MCC). Cytokeratin-20 (CK-20) is used in differential diagnostics of the primary tumour. The aim of this study was to demonstrate the expression of Tn-C in MCC lymph node metastases. Immunohistochemical staining was performed for five metastatic lymph nodes using a monoclonal antibody against Tn-C and CK-20. All five metastatic lymph nodes expressed Tn-C. The expression concentrated around the vascular structures, invasion borders and fibrotic septae. One of the metastatic lymph nodes was strongly positive for CK-20 while the others showed a focal or negative pattern. The normal lymphoid tissue was negative for Tn-C. Tn-C detected metastatic MCC tissue within the lymph nodes undisputedly. There was a clear distinction between the metastatic and normal lymphatic tissue. Furthermore, invasion to the surrounding tissue was easily demonstrated. Contrary to previous studies, CK-20 expression seemed to fluctuate.