血管内皮生长因子C的研究进展

区域淋巴结转移是大多数肿瘤的重要愈后因素,抗淋巴管转移的治疗是目前的研究热点之一,但迄今为止人们对淋巴转移机制了解甚少.血管内皮生长因子C（vascular endothelial growth factor-C,VEGF-C）是第一个被发现的促淋巴管生成因子,已证实VEGF-C及其受体VEGFR-3 （vascular endothelial growth factor receptor-3）在通过诱导肿瘤淋巴管的生成进而促进区域淋巴结转移中可能起重要作用.因此,VEGF-C/ VEGFR-3信号通路可能在肿瘤的抗淋巴管生成治疗中提供一个新靶区.且在恶性肿瘤中,VEGF-C可能通过结合VEGFR-2和VEGFR-3共同促进肿瘤血管生成.对近年来关于VEGF-C与肿瘤淋巴管、血管转移的关系及抗淋巴管生成治疗的研究进行综述.     

非小细胞肺癌组织中VEGF-C和VEGFR-3的表达及其临床意义

背景与目的:血管内皮生长因子-C(vascularendothelialgrowthfactorC,VEGF-C)和VEGFR-3是促进恶性肿瘤淋巴管形成的重要因子,其表达与恶性肿瘤的淋巴结转移关系密切。本文旨在研究VEGF-C和VEGFR-3蛋白在非小细胞肺癌(non-smallcelllungcancer,NSCLC)组织中的表达及其临床意义。方法:应用免疫组化方法检测77例NSCLC组织中VEGF-C和VEGFR-3表达情况,分析其与肿瘤淋巴管密度(lymphaticvesseldensity,LVD)、肿瘤的大小、癌的组织类型、组织分化程度、淋巴结转移情况、临床复发和术后生存期的关系。结果:77例NSCLC组织中有45例(58%)VEGF-C阳性,32例(42%)VEGFR-3阳性。NSCLC组织中VEGF-C表达与肿瘤组织的分化程度有关(r=-0.32,P=0.018);VEGF-C及VEGFR-3表达与肿瘤的淋巴结转移、LVD、肿瘤大小及术后生存期有关。NSCLC组织中VEGF-C与VEGFR-3表达相关(r=0.23,P=0.045)。结论:VEGF-C和VEGFR-3表达与NSCLC的淋巴结转移、预后相关,它的高表达提示肺癌患者容易出现淋巴结转移和预后不良。     

VEGF-C 及VEGFR-3 在肝细胞癌中的表达

 目的　探讨VEGF-C、VEGFR-3、微血管密度（MVD）、微淋巴管密度（LVD）及肝细胞癌临床病理特征之间的关系。方法　取肝细胞癌组织标本60例，正常肝组织标本20例。采用反转录聚合酶链反应（RT-PCR）方法分析其中VEGF-C及VEGFR-3 mRNA 的表达，以免疫组织化学法检测肝癌MVD及LVD，并分析四者与肝癌临床病理特点之间的关系。结果　肝癌组织VEGF-C、VEGFR-3 mRNA表达、MVD及LVD高于正常肝组织（P＜0.01）；肝癌组织中，VEGF-C与VEGFR-3表达、MVD及LVD均呈正相关（P＜0.01），VEGF-C及VEGFR-3表达与肝癌肝内转移、门静脉癌栓形成及淋巴转移相关（P＜0.01），MVD与肝癌肝内转移、门静脉癌栓形成相关（P＜0.01），LVD与淋巴转移相关（P＜0.01）。结论　肝细胞癌组织中VEGF-C及VEGFR-3表达增多，可能通过参与血管、淋巴管生成促进肿瘤的侵袭、转移。     

Suppression of tumor lymphangiogenesis and lymph node metastasis by blocking vascular endothelial growth factor receptor 3 signaling

BACKGROUND: Vascular endothelial growth factor C (VEGF-C) stimulates tumor lymphangiogenesis (i.e., formation of lymphatic vessels) and metastasis to regional lymph nodes by interacting with VEGF receptor 3 (VEGFR-3). We sought to determine whether inhibiting VEGFR-3 signaling, and thus tumor lymphangiogenesis, would inhibit tumor metastasis. METHODS: We used the highly metastatic human lung cancer cell line NCI-H460-LNM35 (LNM35) and its parental line NCI-H460-N15 (N15) with low metastatic capacity. We inserted genes by transfection and established a stable N15 cell line secreting VEGF-C and a LNM35 cell line secreting the soluble fusion protein VEGF receptor 3-immunoglobulin (VEGFR-3-Ig, which binds VEGF-C and inhibits VEGFR-3 signaling). Control lines were transfected with mock vectors. Tumor cells were implanted subcutaneously into severe combined immunodeficient mice (n = 6 in each group), and tumors and metastases were examined 6 weeks later. In another approach, recombinant adenoviruses expressing VEGFR-3-Ig (AdR3-Ig) or beta-galactosidase (AdLacZ) were injected intravenously into LNM35 tumor-bearing mice (n = 14 and 7, respectively). RESULTS: LNM35 cells expressed higher levels of VEGF-C RNA and protein than did N15 cells. Xenograft mock vector-transfected LNM35 tumors showed more intratumoral lymphatic vessels (15.3 vessels per grid; 95% confidence interval [CI] = 13.3 to 17.4) and more metastases in draining lymph nodes (12 of 12) than VEGFR-3-Ig-transfected LNM35 tumors (4.1 vessels per grid; 95% CI = 3.4 to 4.7; P<.001, two-sided t test; and four lymph nodes with metastases of 12 lymph nodes examined). Lymph node metastasis was also inhibited in AdR3-Ig-treated mice (AdR3-Ig = 0 of 28 lymph nodes; AdLacZ = 11 of 14 lymph nodes). However, metastasis to the lungs occurred in all mice, suggesting that LNM35 cells can also spread via other mechanisms. N15 tumors overexpressing VEGF-C contained more lymphatic vessels than vector-transfected tumors but did not have increased metastatic ability. CONCLUSIONS: Lymph node metastasis appears to be regulated by additional factors besides VEGF-C. Inhibition of VEGFR-3 signaling can suppress tumor lymphangiogenesis and metastasis to regional lymph nodes but not to lungs.     

Vascular endothelial growth factor-D is an independent prognostic factor in epithelial ovarian carcinoma

We assessed the presence of vascular endothelial growth factor (VEGF)-C, VEGF-D and their receptor VEGFR-3 by immunohistochemistry in 59 epithelial ovarian carcinomas, 11 borderline tumours and 20 benign cystadenomas. VEGF-C and VEGF-D were generally expressed in tumour cells and also in endothelia adjacent to tumour nests which showed a strong staining for them. VEGFR-3 was expressed in lymphatic and vascular endothelial cells adjacent to tumour nests. Immunoreactivity was significantly more frequent as lesions progressed from a benign tumour to advanced carcinoma. A strong correlation was found between VEGF-C and VEGF-D detected in carcinoma and VEGFR-3 detected in neighbouring endothelial cells. Increased expression of VEGF-C, VEGF-D and VEGFR-3 was significantly associated with lymph node metastasis and peritoneal metastasis outside the pelvis. There was a significant correlation between the high levels of VEGF-C and VEGF-D proteins, and poor survival. The presence of VEGF-D was an independent prognostic indicator by multivariate analysis. We conclude that VEGF-C, VEGF-D and VEGFR-3 play an important role in lymphatic spread and intraperitoneal tumour development in ovarian carcinoma. Since VEGF-D was found to be an independent predictor of poor outcome, its measurement, together with other prognostic markers may improve prospective identification of patients with a poor prognosis.     

Expression of vascular endothelial growth factors-C and -D correlate with evidence of lymphangiogenesis and angiogenesis in pancreatic adenocarcinoma

Background: We analyzed the intratumoral and peritumoral microvessel density (MVD) and microlymphatic vessel density (MLVD) in pancreatic adenocarcinoma (PAC) and recorded the expression of vascular endothelial growth factor (VEGF)-C and -D. These data were tested for their significance for tumor progression. Methods: The tissue samples were obtained from 30 patients with PAC. The expression of VEGF-C and -D, MLVD, MVD was assayed by immunohistochemical staining. The expression of VEGF-A and -C, and -D mRNA was detected by semi-quantitative RT-PCR. Results: Immunohistochemical analysis revealed the presence of VEGF-C and -D immunoreactivity in 73% (22/30) and 57% (17/30). The positive rates of VEGF-C and -D protein in central portion of tumors (30% and 16.7%) were significantly lower than those in marginal portion (73.3% and 56.7%). The group with high expression of VEGF-C and -D in marginal portion had higher incidence of lymph node metastasis, lymphatic invasion and venous invasion. The MLVD in both of the VEGF-C and -D positive groups was higher than that in the negative groups, and the lymph node metastasis increased. MVD in the VEGF-C positive group was higher than that in the negative group. Conclusions: The expression of VEGF-C and -D in the marginal portion of tumor significantly associated with lymphatic metastasis and prognosis in patients with PAC, and may induced lymphangiogenesis. VEGF-C was important in the regulation of angiogenesis and lymphangiogenesis in PAC.     

血管内皮生长因子C、D在鼻咽癌组织中的表达及其临床意义

背景与目的:血管内皮生长因子C(vascular endothelial growth factor-C,VEGF-C)和D(vascular endothelial growth factor-D,VEGF-D)是目前已鉴定出的淋巴管生长因子,有研究表明肿瘤组织中VECF-C或VEGF-D过表达与淋巴转移有关.本研究旨在探讨鼻咽癌组织中VEGF-C和VEGF-D的表达情况及其临床意义.方法:采用免疫组化SP法检测66例鼻咽癌组织中VEGF-C和VEGF-D的表达情况,同时检测血管内皮生长因子受体3(vascular endotheliaI growth factor receptor-3,VEGFR-3)和CD34染色情况并计数微淋巴管密度(lymphatic microvessel density,LMVD)和微血管密度(microvessel density,MVD).结果:VEGF-C高表达率在鼻咽癌组织中(54.5%)较鼻咽非肿瘤组织中(26.3%)高(P＜0.05);鼻咽癌伴区域淋巴结转移或T分期晚者,VEGF-C高表达率增高,单因素及多因素Logistic回归分析均表明区域淋巴结转移与VEGF-C高表达相关(P＜0.05),但VEGF-C高表达与性别、年龄、5年生存率、LMVD、MVD等因素无关(P＞0.05).VEGF-D阳性表达率在鼻咽癌组织中(69.7%)较鼻咽非肿瘤组织中(42.1%)高(P＜0.05);鼻咽癌中VEGF-D阳性表达与性别、年龄、T分期、区域淋巴结转移、LMVD、MVD等因素无关(P＞0.05),但与VEGF-C高表达显著正相关(P＜0.01),VEGF-D阳性表达者5年生存率(50.0%)显著低于VEGF-D不表达者(85.0%)(P＜0.01).结论:鼻咽癌中VEGF-C高表达与区域淋巴结转移密切相关;VEGF-D阳性表达与区域淋巴结转移无关,但与VEGF-C高表达正相关,且与5年生存率密切相关.     

口腔癌VEGF-CmRNA表达和血管及淋巴管生成与淋巴道转移关系的研究

背景与目的VEGF-C与癌周的淋巴管血管生成以及肿瘤的淋巴道转移可能有密切的关系,本研究探讨口腔鳞癌组织血管、淋巴管密度与VEGF-CmRNA表达及淋巴道转移的关系.方法VEGF-C逆转录PCR(RT-PCR),血管、淋巴管酶组化染色、光镜及图像分析观察血管、淋巴管总体面数密度(TNa).结果VEGF-CmRNA表达阳性的淋巴管TNa(26.42±5.85)明显高于阴性淋巴管TNa(17.34±6.48)(P<0.01);VEGF-CmRNA表达阳性的血管TNa(35.16±15.55)略高于阴性的血管TNa(33.49±13.73)(P>0.05).淋巴结转移组血管TNa(44.19±14.29)比无淋巴结转移组TNa(30.61±11.82)增加(P<0.01)、淋巴结转移组淋巴管TNa(30.67±5.76)比无淋巴结转移组TNa(21.94±5.84)增加(P<0.01).结论VEGF-C主要介导了癌周淋巴管生成,对血管生成有一定影响;血管、淋巴管密度的同时增加可能与VEGF、VEGF-C及其受体的协同表达有一定关系.     

VEGF-A和VEGF-C在乳腺癌组织中的表达及其意义

背景与目的:VEGF家族都与血管生成相关,血管内皮生长因子-A(vascularendothelialgrowthfactorA,VEGF-A)和血管内皮生长因子-C(vascularendothelialgrowthfactorC,VEGF-C)与肿瘤的生长和转移关系密切。本研究探讨乳腺癌组织中VEGF-A、VEGF-C的表达与癌细胞增殖、微血管密度(microvesseldensity,MVD)和淋巴结转移的关系。方法:采用免疫组织化学方法观察98例乳腺癌组织中VEGF-A、VEGF-C、增殖细胞核抗原(proliferatingcellnuclearantigen,PCNA)、CD34的表达情况。结果:98例乳腺癌组织中,VEGF-A阳性率为85.7%(84/98),VEGF-C阳性率90.8%(89/98),两者在淋巴结转移组表达均高于未转移组,差异具有显著性(P<0.05)。PCNA的表达随着VEGF-A、VEGF-C表达强度增强,肿瘤细胞增殖活性也随之增强(r=0.432,P=0.000;r=0.294,P=0.001)。淋巴结转移组MVD值(64.26±26.40)明显高于未转移组(50.29±29.35)(P<0.05),且随着VEGF-A表达增强,MVD也随之增高(r=0.327,P<0.001),VEGF-C表达与MVD无相关性(r=0.123,P>0.05)。结论:VEGF-A主要介导了血管生成、细胞增殖和转移;VEGF-C促进乳腺癌细胞增殖,与血管密度无关,与淋巴结转移密切相关。     

VEGF-C和VEGFR-3在鼻咽癌组织中的表达及其意义

目的探讨血管内皮生长因子C（VEGF-C）及其受体3（VEGFR-3）在鼻咽癌淋巴管生成及淋巴道转移中的作用。方法取61例鼻咽癌组织样本,应用免疫组织化学法观察VEGF-C和VEGFR-3在鼻咽癌组织中的表达,应用D2-40标记淋巴管,检测鼻咽癌组织中的微淋巴管密度。结果 61例鼻咽癌组织中,VEGF-C阳性表达率为61.8%,VEGFR-3表达的阳性率为69.1%。经计数淋巴管数量,癌组织中的微淋巴管密度（LVD）与VEGF-C、VEGFR-3的表达显著相关（P〈0.01）。结论 VEGF-C通过与VEGFR-3的结合促进癌组织中淋巴管生成,使癌组织中LVD增高,从而对肿瘤细胞发生淋巴道转移起促进作用。     

Vascular endothelial growth factor C promotes tumor lymphangiogenesis and intralymphatic tumor growth

Many solid tumors produce vascular endothelial growth factor C (VEGF-C), and its receptor, VEGFR-3, is expressed in tumor blood vessels. To study the role of VEGF-C in tumorigenesis, we implanted MCF-7 human breast carcinoma cells overexpressing recombinant VEGF-C orthotopically into severe combined immunodeficient mice. VEGF-C increased tumor growth, but unlike VEGF, it had little effect on tumor angiogenesis. Instead, VEGF-C strongly promoted the growth of tumor-associated lymphatic vessels, which in the tumor periphery were commonly infiltrated with the tumor cells. These effects of VEGF-C were inhibited by a soluble VEGFR-3 fusion protein. Our data suggest that VEGF-C facilitates tumor metastasis via the lymphatic vessels and that tumor spread can be inhibited by blocking the interaction between VEGF-C and its receptor.     

The tyrosine kinase inhibitor cediranib blocks ligand-induced vascular endothelial growth factor receptor-3 activity and lymphangiogenesis

Solid tumors express a range of factors required to sustain their growth and promote their dissemination. Among these are vascular endothelial growth factor-A (VEGF-A), the key angiogenic stimulant, and VEGF-C, a primary mediator of lymphangiogenesis. Small molecule tyrosine kinase inhibitors offer the potential to inhibit more than one kinase and impede tumor growth by multiple mechanisms. However, their potency toward individual targets can vary. Cediranib (RECENTIN; AZD2171) is an inhibitor of VEGF signaling that has been shown in experimental models to prevent VEGF-A-induced angiogenesis and primary tumor growth, yet the effects of cediranib on VEGF receptor (VEGFR)-3-mediated endothelial cell function and lymphangiogenesis are unknown. To better understand the activity of cediranib against VEGFR-3 and its associated signaling events compared with its activity against VEGFR-2, we used the receptor-specific ligands VEGF-E and VEGF-C156S. In human endothelial cells, cediranib inhibited VEGF-E-induced phosphorylation of VEGFR-2 and VEGF-C156S-induced phosphorylation of VEGFR-3 at concentrations of 相似文献   

卵巢交界性肿瘤血管内皮生长因子表达和微血管密度的研究

背景与目的:血管生成是实体肿瘤生长、侵袭、扩散转移的关键,微血管密度(microvesselofdensity,MVD)可反映肿瘤的血管形成情况。血管内皮生长因子(vascularendothelialgrowthfactor,VEGF)是具有重要意义的促血管生长因子,它与肿瘤的生长密切相关。本研究检测卵巢交界性肿瘤组织中VEGF的表达和MVD,探讨它们与临床病理特征及预后的关系。方法:采用免疫组化SP法和原位杂交技术检测69例卵巢交界性肿瘤、18例卵巢良性肿瘤和27例卵巢恶性肿瘤组织中VEGF蛋白及VEGFmRNA的表达,用FⅧ因子单克隆抗体标记新生血管内皮,计数并计算MVD。结果:VEGF蛋白、VEGFmRNA在卵巢交界性肿瘤组织中的表达均介于卵巢良性肿瘤与卵巢恶性肿瘤之间,其结果差异均有显著性(P<0.05);也与卵巢交界性肿瘤的临床分期、MVD值密切相关(P<0.05);但VEGF与卵巢交界性肿瘤的组织分型、有无腹腔种植无关(P>0.05)。结论:VEGF与卵巢肿瘤的生长、侵袭、转移密切相关;检测VEGF有助于判断卵巢肿瘤的恶性程度,为判断卵巢交界性肿瘤患者的预后提供依据。     

宫颈癌中iNOS的表达与肿瘤新生淋巴管及VEGF-C的关系

目的:探测人宫颈癌中的诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)、血管内皮生长因子-C(vascular endothelial growth factor,VEGF-C)的表达与D2-40标记的淋巴管密度的关系.方法:采用免疫组化SP法检测宫颈鳞状细胞癌中iNOS、VEGF-C的表达情况,并用D2-40进行癌组织淋巴管染色,测定其淋巴管密度(lymphatic vessel density,LVD),另取正常宫颈组织10例作对照,观察上述因子在宫颈癌及正常宫颈中的表达及其与肿瘤病理参数之间的相关性.结果:与正常宫颈组织相比,宫颈癌组织中具有更高的iNOS、VEGF-C的表达率及淋巴管密度(t=2.39、3.08,P=0.021、0.003).与无淋巴结转移组相比,淋巴结转移组具有更高的iNOS、VEGF-C阳性表达率(P =0.044、0.035)及淋巴管密度(t=3.79,P＜0.001);iNOS、VEGF-C阳性共表达与肿瘤淋巴结转移之间存在正相关(P=0.046),宫颈癌组织中iNOS、VEGF-C的表达具有相关性(P＜0.001).结论:iNOS、VEGF-C在宫颈癌组织中呈过表达,其与宫颈癌的淋巴转移关系密切;iNOS可能通过催化产生NO上调VEGF-C的表达,诱导肿瘤淋巴管生成,导致宫颈癌的淋巴道转移.iNOS、VEGF-C均参与宫颈的发展、浸润和转移,可作为评估宫颈癌的生物学行为和判断预后的指标.针对iNOS、VEGF-C的靶向治疗可成为宫颈癌治疗的新靶点.     

The effect of the expression of vascular endothelial growth factor (VEGF)-C and VEGF receptor-3 on the clinical outcome in patients with gastric carcinoma

Aims

We aimed to investigate the relationship among VEGF-C/VEGFR-3 expression, lymphatic metastasis and patient prognosis in gastric carcinoma.

Material and methods

VEGF-C and VEGFR-3 expression in gastric carcinoma tissues obtained from 204 patients who underwent curative gastrectomy (105 cases presented with lymph node metastasis and 99 cases without metastasis) was examined immunohistochemically. There was no significant difference in the other clinicopathologic variables except for postoperative pathological tumor stage (pT) and TNM stage between the two groups. The results were statistically processed.

Results

The results showed that VEGF-C was located mainly in the cytoplasm of tumor cells and VEGFR-3 was found predominantly in the endothelium of lymphatic vessels. VEGF-C and VEGFR-3 expression was more frequent in gastric carcinoma tissues than that in normal gastric tissues, 54.90% and 35.29% respectively, which revealed that the expression of VEGF-C and VEGFR-3 was significantly stronger in patients with lymph node metastasis than in those without metastasis. Patients who had positive staining for VEGF-C showed significantly less favorable survival rates compared with patients who had negative staining for VEGF-C. The survival rates of patients who had positive staining for VEGFR-3 also were significantly lower compared with patients who had negative staining for VEGFR-3. Patients who had positive staining for both VEGF-C and VEGFR-3 exhibited the most unfavorable prognosis. Multivariate analysis demonstrated that the expression of VEGF-C and VEGFR-3 was an independent prognostic determinant. In addition, faint to moderate VEGF-C expression was detected in normal gastric epithelial cells (18/204, 8.9%).

Conclusions

VEGF-C and VEGFR-3 expression could serve as a prognostic biomarker in patients with gastric carcinoma.     

VEGF-C和VEGFR-3对乳腺癌淋巴管生成和淋巴结转移的影响

目的:探讨VEGF-C及VEGFR-3对乳腺癌淋巴结转移的影响。方法:采用免疫组化SP法检测乳腺病、乳腺纤维腺瘤和乳腺癌中VEGF-C及VEGFR-3的表达状态。结果:10例乳腺病及纤维腺瘤VEGF-C均阴性,也无VEGFR-3阳性淋巴管;48例乳腺癌组织VEGF-C阳性率为70.83%(34/48);淋巴结转移者VEGF-C阳性率为92.59%(25/27),显著高于无转移者(42.86%,9/21)(P<0.01)。VEGFR-3阳性淋巴管条数随VEGF-C强度增强而增多。在淋巴结转移者中,VEGFR-3阳性淋巴管条数(6.03)多于无淋巴结转移者(2.01)(P<0.01)。结论:乳腺癌组织中VEGF-C的表达状态与VEGFR-3阳性淋巴管数量及淋巴结转移关系密切。     

Relationship between Lymphatic Vessel Density and Lymph Node Metastasis of Invasive Micropapillary Carcinoma of the Breast

OBJECTIVE To investigate the relationship between lymphatic vessel density and lymph node metastasis of invasive micropapillary carcinoma (IMPC) of the breast. METHODS The immunohistochemical study for vascular endothelial growth factor-c (VEGF-C), VEGF Receptor-3 (VEGFR-3) and lymphatic vessel density of 51 cases of IMPC were performed, and lymph node metastases were examined by microscopic analysis of these cases. RESULTS In IMPC, VEGF-C was expressed in the cytoplasm and/or on the membrane of the tumor cells, and the expression of VEGF-C showed a positive correlation with lymph node metastasis (P<0.01). Lymphatic vessel density was determined by the number of micro-lymphatic vessels with VEGFR-3 positive staining. Lymphatic vessel density was positively correlated with VEGF-C expression (P<0.01) and lymph node metastasis (P<0.01). The percentage of IMPC in the tumor was not associated with the incidence of lymph node metastasis. The metastatic foci in lymph nodes were either pure or predominant micropapillary carcinoma. CONCLUSION The results suggested that VEGF-C overexpression stimulated tumor lymphangiogenesis, and the increased lymphatic vessel density may be the key factor that influenced lymph node metastasis of IMPC.     

Lymphatic vessel density and vascular endothelial growth factor-C expression correlate with malignant behavior in human pancreatic endocrine tumors.

Metastatic dissemination of tumor cells to regional lymph nodes is a common early feature of many human cancers including pancreatic adenocarcinoma. In contrast, lymph node metastasis is more variably observed in pancreatic endocrine tumors. The objective of this study was to assess the lymphatic system of human pancreatic endocrine tumors and correlate this to clinical behavior. Immunohistochemistry was performed using antibodies to two recently identified markers of lymphatic endothelium, namely, LYVE-1 and podoplanin, and to the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C. As has been reported previously, we observed that in the normal pancreas, islets of Langerhans are devoid of intra-islet lymphatics, but that lymphatics are present in connective tissue in association with ducts and blood vessels. We found that both benign and malignant pancreatic endocrine tumors contain intratumoral lymphatic vessels. Lymphatic vessel density was related to the size of the tumor in benign tumors and to the presence of liver metastasis but not to lymph node metastasis in malignant tumors. VEGF-C was expressed in tumor cells: 4 of 19 (21%) benign tumors were positive, whereas 6 of 9 (67%) borderline tumors and 9 of 11 (82%) carcinomas were positive. These findings strongly suggest that lymphangiogenesis occurs in pancreatic endocrine tumors and that lymphatic invasion and the development of metastases are associated with VEGF-C expression.