Transgenic induction of vascular endothelial growth factor-C is strongly angiogenic in mouse embryos but leads to persistent lymphatic hyperplasia in adult tissues

Vascular endothelial growth factor-C (VEGF-C) is the quintessential lymphangiogenic growth factor that is required for the development of the lymphatic system and is capable of stimulating lymphangiogenesis in adults by activating its receptor, VEGFR-3. Although VEGF-C is a major candidate molecule for the development of prolymphangiogenic therapy for defective lymphatic vessels in lymphedema, the stability of lymph vessels generated by exogenous VEGF-C administration is not currently known. We studied VEGF-C-stimulated lymphangiogenesis in inducible transgenic mouse models in which growth factor expression can be spatially and temporally controlled without side effects, such as inflammation. VEGF-C induction in adult mouse skin for 1 to 2 weeks caused robust lymphatic hyperplasia that persisted for at least 6 months. VEGF-C induced lymphangiogenesis in numerous tissues and organs when expressed in the vascular endothelium in either neonates or adult mice. Very few or no effects were observed in either blood vessels or collecting lymph vessels. Additionally, VEGF-C stimulated lymphangiogenesis in embryos after the onset of lymphatic vessel development. Strikingly, a strong angiogenic effect was observed after VEGF-C induction in vascular endothelium at any point before embryonic day 16.5. Our results indicate that blood vessels can undergo VEGF-C-induced angiogenesis even after down-regulation of VEGFR-3 in embryos; however, transient VEGF-C expression in adults can induce long-lasting lymphatic hyperplasia with no obvious side effects on the blood vasculature.     

Tumor lymphangiogenesis: a novel prognostic indicator for cutaneous melanoma metastasis and survival

Malignant melanomas of the skin are distinguished by their propensity for early metastatic spread via lymphatic vessels to regional lymph nodes, and lymph node metastasis is a major determinant for the staging and clinical management of melanoma. However, the importance of tumor-induced lymphangiogenesis for lymphatic melanoma spread has remained unclear. We investigated whether tumor lymphangiogenesis occurs in human malignant melanomas of the skin and whether the extent of tumor lymphangiogenesis may be related to the risk for lymph node metastasis and to patient survival, using double immunostains for the novel lymphatic endothelial marker LYVE-1 and for the panvascular marker CD31. Tumor samples were obtained from clinically and histologically closely matched cases of primary melanomas with early lymph node metastasis (n = 18) and from nonmetastatic melanomas (n = 19). Hot spots of proliferating intratumoral and peritumoral lymphatic vessels were detected in a large number of melanomas. The incidence of intratumoral lymphatics was significantly higher in metastatic melanomas and correlated with poor disease-free survival. Metastatic melanomas had significantly more and larger tumor-associated lymphatic vessels, and a relative lymphatic vessel area of >1.5% was significantly associated with poor disease-free and overall survival. In contrast, no differences in the density of tumor-associated blood vessels were found. Vascular endothelial growth factor and vascular endothelial growth factor-C expression was equally detected in a minority of cases in both groups. Our results reveal tumor lymphangiogenesis as a novel prognostic indicator for the risk of lymph node metastasis in cutaneous melanoma.     

人参皂甙Rh2对小鼠移植瘤血管内皮生长因子C及淋巴管生成的影响

目的 观察人参皂甙Rh2对小鼠移植瘤生长,肿瘤细胞血管内皮生长因子c(VEGF-C)表达和淋巴管密度的影响,探讨其作用机制.方法 用S180瘤株构建55只小鼠移植瘤模型,成瘤后灌服人参皂甙Rh2,观察用药组与对照组移植瘤的生长情况,免疫组织化学染色,比较用药2周、3周后癌细胞VEGF-C的表达及LYVE-1标记的淋巴管密度与对照组的差异.结果接种约第3周开始,对照组移植瘤生长速度明显快于用药组.用药第2周癌细胞VEGF-C表达及淋巴管密度与对照组无差异;第3周VEGF-C表达较对照组弱,淋巴管密度也较对照组低,有差异(P<0.05). 结论 人参皂甙Rh2能抑制肿瘤生长,降低淋巴管密度,其机制可能是通过降低VEGF-C在癌细胞的表达,干扰淋巴管的生成.     

VEGF-C在卵巢癌局部淋巴结内淋巴管生成中的作用

目的观察血管内皮生长因子-C(VEGF-C)在卵巢癌组织内的表达,分析其与卵巢癌局部淋巴结内淋巴管生成之间的关系。方法取卵巢癌64例,其中,有淋巴结转移40例,无淋巴结转移24例。应用免疫组化法和Western blot技术观察VEGF-C在卵巢癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,检测卵巢癌局部淋巴结内淋巴管生成情况。结果 VEGF-C主要表达于卵巢癌细胞浆和胞膜以及癌组织周围浸润的炎性细胞,在有淋巴结转移组的表达率明显高于其在无淋巴结转移组的表达率。Western blot检测结果表明,VEGF-C蛋白在有淋巴结转移的卵巢癌组织中的表达量高于其在无淋巴结转移的卵巢癌组织内的表达量。D2-40表达于卵巢癌局部淋巴结内的淋巴管内皮细胞,在有转移的淋巴结内可见大量新生的淋巴管,淋巴管腔内存在入侵的肿瘤细胞,在无转移的淋巴结内观察到新生的淋巴管。在无淋巴结转移组病例中,卵巢癌组织VEGF-C阳性者局部淋巴结内淋巴管密度明显高于VEGF-C阴性者淋巴结内的淋巴管密度。结论 VEGF-C的表达与卵巢癌淋巴结转移密切相关,卵巢癌在发生局部淋巴结转移之前存在淋巴结内淋巴管生成的现象,卵巢癌组织内VEGF-C的表达在卵巢癌局部淋巴结内的淋巴管生成中可能发挥重要作用。     

Lymphangiogenesis and lymphatic metastasis in breast cancer

Lymphatic metastasis is the main prognostic factor for survival of patients with breast cancer and other epithelial malignancies. Mounting clinical and experimental data suggest that migration of tumor cells into the lymph nodes is greatly facilitated by lymphangiogenesis, a process that generates new lymphatic vessels from pre-existing lymphatics with the aid of circulating lymphatic endothelial progenitor cells. The key protein that induces lymphangiogenesis is vascular endothelial growth factor receptor-3 (VEGFR-3), which is activated by vascular endothelial growth factor-C and -D (VEGF-C and VEGF-D). These lymphangiogenic factors are commonly expressed in malignant, tumor-infiltrating and stromal cells, creating a favorable environment for generation of new lymphatic vessels. Clinical evidence demonstrates that increased lymphatic vessel density in and around tumors is associated with lymphatic metastasis and reduced patient survival. Recent evidence shows that breast cancers induce remodeling of the local lymphatic vessels and the regional lymphatic network in the sentinel and distal lymph nodes. These changes include an increase in number and diameter of tumor-draining lymphatic vessels. Consequently, lymph flow away from the tumor is increased, which significantly increases tumor cell metastasis to draining lymph nodes and may contribute to systemic spread. Collectively, recent advances in the biology of tumor-induced lymphangiogenesis suggest that chemical inhibitors of this process may be an attractive target for inhibiting tumor metastasis and cancer-related death. Nevertheless, this is a relatively new field of study and much remains to be established before the concept of tumor-induced lymphangiogenesis is accepted as a viable anti-metastatic target. This review summarizes the current concepts related to breast cancer lymphangiogenesis and lymphatic metastasis while highlighting controversies and unanswered questions.     

Lymphangiogenesis in myocardial remodelling after infarction

AIMS: The lymphatic system is involved in fluid homeostasis of the cardiac interstitium, but lymphangiogenesis in myocardial remodelling has not previously been examined histopathologically. The aim was to investigate by D2-40 immunohistochemistry the sequential changes in lymphatic distribution in the process of myocardial remodelling after myocardial infarction (MI). METHODS AND RESULTS: Myocardial tissues in various phases of healing after MI were obtained from 40 autopsied hearts. D2-40+ lymphatic vessel density (LD) and CD34+ blood vessel density (BD) in the lesion were determined. BD decreased with advance of myocardial necrosis, subsequently increased at the early stage of granulation and thereafter decreased with the progression of scar formation. In contrast, lymphatic vessels were not detected in lesions with coagulation necrosis, and newly formed lymphatics first appeared in the early stages of granulation. A subsequent increase in LD was demonstrated in the late stages of granulation, and lymphatics remained up to the scar phase. Vascular endothelial growth factor-C was consistently expressed in viable cardiomyocytes around the lesion in all of these stages. CONCLUSION: In myocardial remodelling after MI, lymphangiogenesis lags behind blood vessel angiogenesis; newly formed lymphatics may be involved mainly in the maturation of fibrosis and scar formation through the drainage of excessive proteins and fluid.     

Expression of thymosin beta10 and its role in non-small cell lung cancer

The exact role of thymosin beta10 in lung cancer progression remains unclear. We investigated by immunohistochemistry the expression of thymosin beta10 protein in tumors and tumor-adjacent tissues from 69 patients with non-small cell lung cancer. The relationship of thymosin beta10 expression with vascular endothelial growth factor, vascular endothelial growth factor-C, microvessel density, and lymphatic vessel density was determined; clinicopathologic factors and surgical treatment outcome were also studied. The results showed that thymosin beta10 was mainly expressed in the cytoplasm of lung cancer cells, and the overexpression of thymosin beta10 was correlated with advanced clinical stage (P = .026), distant metastases (P = .016), lymph node metastases (P = .007), poor degree of differentiation (P = .03), and poor postoperative survival (P = .004). Furthermore, thymosin beta10 overexpression was associated with vascular endothelial growth factor (P = .004), vascular endothelial growth factor-C (P = .017), microvessel density (P = .000), and lymphatic vessel density (P = .002). The lowest survival rate was observed in the patients with high thymosin beta10, positive vascular endothelial growth factor, and high microvessel density (P = .007) or in the patients with high thymosin beta10, positive vascular endothelial growth factor-C, and high lymphatic vessel density (P = .005). These results suggest that thymosin beta10 might induce microvascular and lymphatic vessel formation by up-regulating vascular endothelial growth factor and vascular endothelial growth factor-C in lung cancer tissues, thus promoting the distant and lymph node metastases and being implicated in the progression of non-small cell lung cancer.     

血管内皮生长因子C和Smad4的表达与膀胱癌淋巴管生成之间的关系

目的观察血管内皮生长因子-C(VEGF-C)和Smad4在膀胱癌的表达,分析VEGF-C和Smad4的表达与膀胱癌淋巴管生成及膀胱癌进展之间的关系。方法取膀胱癌病例56例,其中浅表性膀胱癌(Tis,Ta,T1)32例,浸润性膀胱癌(T2以上)24例。应用免疫组化法和Western blot技术观察VEGF-C和Smad4在膀胱癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,检测膀胱癌组织内的淋巴管密度(LVD)。结果VEGF-C表达于肿瘤细胞的胞浆内,Smad4表达于肿瘤细胞的胞浆和胞核内。VEGF-C的表达水平与膀胱癌淋巴管密度呈正相关(P0.05),Smad4的表达水平与膀胱癌淋巴管密度呈负相关(P0.05)。VEGF-C和Smad4的表达呈负相关,VEGF-C的高表达和Smad4的低表达与膀胱癌淋巴管生成之间呈显著的相关性。Western blot检测结果表明,VEGF-C在浸润性膀胱癌组织内的表达量与其在浅表性膀胱癌组织内的表达量未见显著差异(P0.05),而Smad4在浅表性膀胱癌组织内的表达量明显高于其在浸润性膀胱癌组织内的表达量(P0.05)。结论 VEGF-C和Smad4在膀胱癌组织内表达水平呈负相关,Smad4可能通过调节VEGF-C蛋白的表达而抑制膀胱癌淋巴管生成。     

Stromal impact on tumor growth and lymphangiogenesis in human carcinoma xenografts

Squamous cell carcinomas (SCCs) arising in the oral cavity are associated with poor survival, mainly due to metastatic disease. In contrast, skin SCCs rarely metastasize and are usually curable. To study influence of tongue and skin stroma on cancer growth and induction of lymphangiogenesis, xenograft tumors of human carcinoma cells were established either in tongue or skin of BALB/c nude mice. Two oral and two skin SCC cell lines were used, as well as an endometrial adenocarcinoma cell line. Tongue tumors established from all cell lines were larger than corresponding skin tumors. Peritumoral lymphatic vessel density was up to five times higher in tongue than in corresponding skin tumors, and mRNA level of the lymphangiogenic growth factor vascular endothelial growth factor (VEGF)-C was twice as high in tongue tumors compared with corresponding skin tumors. Contrary to lymphatic vessel density, blood vessel density was higher in skin tumors than in tongue tumors. In a cohort of patient samples, lymphatic vessel density was found to be higher in tongue SCCs compared with skin SCCs, supporting a clinical relevance of our findings. Our results show that the tumor stroma has a profound impact on cancer growth and induction of lymphangiogenesis and angiogenesis. The difference in lymphatic vessel density between tongue and skin tumors may be important in directing metastatic potential of tumors arising in these organs.     

The extent of retraction clefts correlates with lymphatic vessel density and VEGF-C expression and predicts nodal metastasis and poor prognosis in early-stage breast carcinoma

Although the earliest feature of disseminated disease in breast cancer is regional lymph node involvement, little is known about the mechanisms whereby cancer cells interact with lymphatic endothelial cells and enter the lymphatic system. We have previously reported that the extensive presence of retraction clefts in breast carcinomas highly significantly correlates with lymphatic tumor spread and predicts poor outcome, suggesting that retraction clefts are not just fixation artifacts, but real potential spaces that are exaggerated by tissue processing and may reflect an early stage of lymphatic invasion. In this study, we examined the correlation between the extent of retraction clefts and lymphangiogenesis, as assessed by lymphatic vessel density and vascular endothelial growth factor-C (VEGF-C) expression in a series of 256 early-stage breast carcinomas. The presence and extent of retraction clefts around tumor cell nests was determined by review of all hematoxylin- and eosin-stained tumor sections. Lymphatic vessels were detected by podoplanin immunohistochemistry and lymphatic vessel density was measured using the hot-spot method. The expression of VEGF-C in the tumor cells was determined by immunohistochemistry and analyzed semiquantitatively on a four-tiered scale. High levels of retraction clefts, peritumor lymphatic vessel density and VEGF-C expression at the invasive edge in breast carcinomas significantly correlated with tumor size, histological grade, lymphatic invasion and nodal metastasis. Breast carcinomas showing extensive retraction clefts (>20% of tumor volume) were found to have significantly higher lymphatic vessel density and VEGF-C expression levels compared to tumors without this feature. High retraction clefts, peritumor lymphatic vessel density and VEGF-C expression predicted poor outcome in breast carcinomas. Our results support the hypothesis that retraction clefts are real potential spaces that may represent 'pre-lymphatic spaces' facilitating initial lymphatic invasion and that growth factors secreted by the tumor cells may stimulate tumor-associated lymphangiogenesis by promoting the endothelialization of these 'pre-lymphatic channels'.     

Intratumoral c-Met expression is associated with vascular endothelial growth factor C expression, lymphangiogenesis, and lymph node metastasis in oral squamous cell carcinoma: implications for use as a prognostic marker

Hepatocyte growth factor has been identified as a lymphangiogenic factor in experimental animal models. However, the correlation between hepatocyte growth factor or c-Met expression and lymphangiogenesis in human spontaneous tumors has been rarely reported, and the distribution pattern of c-Met on tumor-related lymphatic vessels remains to be further investigated. Lymphatic vessel density, lymphatic invasion, the expression of hepatocyte growth factor, c-Met, and vascular endothelial growth factor C proteins were evaluated by immunohistochemistry in 76 cases of oral squamous cell carcinoma. The distribution of c-Met on lymphatic endothelium was examined. High expression of c-Met in tumor cells was significantly associated with advanced clinical stage (P = .045), high expression of vascular endothelial growth factor-C (P < .001), higher peritumoral lymphatic vessel density (P = .003), higher incidence of peritumoral lymphatic invasion (P = .032), and positive lymph node status (P = .005), in spite of its negative expression on most lymphatic vessels. Patients with high–c-Met expression tumors exhibited shorter overall survival and disease-free survival (P < .001 and P = .010, respectively). Taken together, our results provide indirect evidence for an association and possible regulatory link of c-Met with the lymphangiogenic factor, vascular endothelial growth factor C, and, by extension, with lymphangiogenesis and lymph node metastasis, suggesting important prognostic significance of c-Met for patients with oral squamous cell carcinoma.     

VEGF-C表达和微淋巴管密度与胃癌淋巴转移的关系及意义

目的探讨胃癌组织血管内皮生长因子C(VEGF-C)表达和微淋巴管密度(MLVD)及两者与胃癌淋巴转移的关系。方法应用免疫组织化学方法检测208例人胃癌组织、40例癌浸润前缘组织及139例人胃正常粘膜组织中VEGF-C、D2-40的表达,对D2-40阳性脉管进行MLVD计数,并结合病理资料进行统计学分析。结果胃癌组织VEGF-C的表达明显高于正常胃粘膜组织(χ2=109.199,P<0.01);胃癌组织中有淋巴结转移(χ2=14.496,P<0.01)或浸润透浆膜(χ2=11.586,P<0.01)组VEGF-C表达水平分别较无转移或浸润未及浆膜组增高。癌浸润前缘组织中MLVD(18.36±15.60个/mm2)明显高于胃癌组(9.41±9.32个/mm2,t=-3.681,P<0.01)和胃正常粘膜组织(7.70±7.69个/mm2,t=-4.180,P<0.01);胃癌淋巴结转移组MLVD(9.81±9.97个/mm2)高于无转移组(6.41±7.85个/mm2,t=2.516,P<0.01),而在浸润透浆膜组(11.20±10.55个/mm2)和未及浆膜组(8.54±9.36个/mm2)MLVD无差别(t=1.467,P=0.472)。另外,在胃癌组织中VEGF-C表达与MLVD呈正相关(F=2.910,P<0.05)。结论VEGF-C在胃癌中的高表达与胃癌浸润深度、淋巴转移密切相关。     

淋巴管内皮细胞体外培养模型的建立

目的建立淋巴管内皮细胞培养模型,为淋巴管生成及肿瘤淋巴管转移等方面的研究提供细胞生物学基础。方法用胶原酶灌注消化的方法,从猪胸导管中分离出淋巴管内皮细胞进行原代及传代培养,应用免疫细胞化学法对培养的细胞进行鉴定。结果原代细胞培养3～5h后,大部分活力较高的内皮细胞已开始贴壁,12～24h后,内皮细胞己铺展形成由数个细胞组成的细胞群,1～2w后,细胞呈生长密集状并汇合形成单层,在倒置相差显微镜下,呈特征性"鹅卵石状"或"铺路石状"镶嵌排列生长。免疫荧光化学检测表明,淋巴管内皮细胞表达Ⅷ因子和血管内皮生长因子受体-3。结论该模型具有体内淋巴管内皮细胞的生物学特性,可用于淋巴管生成及肿瘤淋巴管转移等方面的体外研究。     

Significance of tumor-associated stroma in promotion of intratumoral lymphangiogenesis: pivotal role of a hyaluronan-rich tumor microenvironment

Stromal cells, together with extracellular matrix components, provide a tumor microenvironment that is pivotal for cancer cell growth and progression. In our previous study using a conditional transgenic mouse model of breast cancer, the overproduction of hyaluronan, a major extracellular constituent, accelerated tumor angiogenesis through stromal cell recruitment. This finding led us to investigate the role of hyaluronan in the lymphatic vessel system. Here, we have found that microenvironmental hyaluronan promoted tumor lymphangiogenesis concurrently with the formation of stromal structures. Additionally, lymphatic vessels frequently penetrated and accumulated into stromal compartments, and up-regulation of vascular endothelial growth factor-C and -D was detected at tumor-stromal interfaces. To assess the contribution of stromal cells to lymphangiogenesis in vivo, we established tumor-associated fibroblasts from hyaluronan-overproducing mammary tumors and implanted them together with carcinoma cells from control tumors or MCF-7 human breast carcinoma cells in nude mice. Carcinoma cells grew rapidly in association with marked stromal reactions and lymphangiogenesis. Without the stromal cells, however, the tumors developed slowly with less stroma and lymphatic vessels. These findings underline the significance of tumor-associated stroma in the promotion of intratumoral lymphangiogenesis and suggest a pivotal role for the hyaluronan-rich tumor microenvironment.     

Inhibition of VEGFR-3 activation in tumor-draining lymph nodes suppresses the outgrowth of lymph node metastases in the MT-450 syngeneic rat breast cancer model

For many types of human cancer, the expression of vascular endothelial growth factor-C (VEGF-C) correlates with enhanced tumor-associated lymphatic vessel density, metastasis formation and poor prognosis. In experimental animals, VEGF-C produced by primary tumors can induce lymphangiogenesis within and/or at the periphery of the tumor, and promotes metastasis formation. Tumor-induced lymphangiogenesis is therefore thought to expedite entry of tumor cells into the lymphatic vasculature and their trafficking to regional lymph nodes, thereby fostering metastatic dissemination. Tumour-produced VEGF-C can also drain to the regional lymph nodes and induce lymphangiogenesis there. Whether this activity promotes metastasis formation remains unclear. To address this issue we manipulated VEGF-C activity and VEGFR-3 activation in the lymph nodes draining syngeneic rat breast cancers using intra-dermal delivery of either recombinant VEGF-C or VEGFR-3 blocking antibodies to induce or suppress lymph node lymphangiogenesis, respectively. Recombinant VEGF-C induced lymph node lymphangiogenesis, but was not sufficient to promote metastasis formation by poorly metastatic NM-081 breast tumours. Conversely, inhibition of lymph node lymphangiogeneis induced by highly metastatic MT-450 breast tumours suppressed the outgrowth of lymph node metastases, but not the initial colonization of the lymph nodes. Lung metastasis was also not affected. We conclude that tumor-derived VEGF-C draining to regional lymph nodes promotes the outgrowth of lymph node metastases. VEGF-C may induce lung metastasis independently of its effects on lymph node metastasis.     

Lymphatic spread is related to VEGF-C expression and D2-40-positive myofibroblasts in intrahepatic cholangiocarcinoma.

Lymph node metastasis via lymphatic vessels is related with an adverse outcome in many tumors. It is unclear whether lymphatic spread needs the development of the new lymphatic vessels or the expression of lymphangiogenetic factor in intrahepatic cholangiocarcinoma. The aim of this study was to assess the role of lymphangiogenesis, vascular endothelial growth factor-C (VEGF-C) expression, and D2-40-positive myofibroblastic cells for lymphatic spread and patient outcome in 88 cases of intrahepatic cholangiocarcinoma. We also assessed VEGF-C expression in 15 cases of metastatic lymph nodes. There was a significant correlation between lower lymphatic vessel density in the tumor center and positive lymphatic invasion (P=0.0100). Poorly differentiated cholangiocarcinoma showed higher lymphatic vessel density in the tumor periphery and in the peritumoral area (P=0.0315 and P=0.0360, respectively). Lymphatic invasion was observed higher in the peritumoral area (63%, 24/38) and in the tumor periphery (79%, 30/38) than in the tumor center (27%, 9/38). There was no significant correlation between the proliferative lymphatic vessels and pathologic features; however, lymphatic invasion was significantly associated with VEGF-C expression (P=0.0006), and the VEGF-C expression was seen in 12 of 15 cases (80%) of metastatic lymph node. Nodal metastasis was correlated with D2-40-positive myofibroblasts (P=0.0161). VEGF-C expression was an independent prognostic factor by multivariate survival analysis (P=0.0131). Our findings suggest that VEGF-C has an important role in lymphatic invasion via the preexisting lymphatic vessels in the tumor margin, and that lymphangiogenesis does not play a direct role in lymphatic metastasis. D2-40-positive myofibroblasts may contribute to lymphatic metastasis.     

Expression of vascular endothelial growth factor-C and its receptor in invasive micropapillary carcinoma of the breast

Invasion to lymphatic vessels and metastasis to lymph nodes are frequent complications in invasive micropapillary carcinoma (IMPC) of human breast cancer. Vascular endothelial growth factor-C (VEGF-C) and its receptor, VEGFR-3 have been implicated as the important factors in the formation of lymphatic vessels and recent experimental evidence strongly suggests that lymphangiogenesis in tumor promotes lymphatic metastasis. To clarify the mechanism of its occurrence, the expression of VEGF-C, VEGFR-3 and lymphatic vessel density (LVD) was examined in 40 cases of IMPC (pure and mixed type) and in 40 cases of pseudo-IMPC. Cytoplasmic expression of VEGF-C and VEGFR-3 were more frequent in tumor cells of IMPC compared to those of pseudo-IMPC. A significant positive correlation was found between the expression of VEGF-C and VEGFR-3 in both IMPC and pseudo-IMPC. The expression of VEGF-C was also significantly associated with higher peritumoral LVD, lymphatic invasion and number of lymph node metastasis in IMPC. These findings suggest that VEGF-C promotes the proliferation of peritumoral lymphatic vessels and that lymphatic invasion and metastasis to lymph nodes are frequently induced in IMPC of breast.