title: A low frequency of lymph node metastasis in clear-cell renal cell carcinoma is related to low lymphangiogenic activity.
abstract: OBJECTIVE
  To assess ongoing lymphangiogenesis in renal cell carcinoma (RCC) by histomorphometry and by quantifying mRNA expression levels of lymphangiogenesis-related factors.
  
  
  METHODS
  Using D2-40 antibody as a lymphatic marker, lymph vessels were counted in tissue sections of 150 clear-cell RCCs (ccRCC) and 61 non-neoplastic controls, using the Chalkley method, which measures the relative lymph vessel area (LVA). Double-staining with Ki67 and D2-40 was used to assess active lymphangiogenesis. In a subset of 25 ccRCCs and nine non-neoplastic controls mRNA expression levels of lymphangiogenic factors were determined by real-time quantitative reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  LVA was higher in normal renal tissue than in both intra- and peri-tumoral LVA (P < 0.001). LVA in the tumour periphery was higher than in the tumour parenchyma (P < 0.001). Lymphatic endothelial cell proliferation (LECP) was identified in 8.2% of the control sections and was higher than the intratumoral LECP fraction (LECP%, 2.6%; P = 0.02) and the peritumoral LECP% (6.5%; P > 0.05). Compared with controls, ccRCC specimens had higher mRNA expression levels of vascular endothelial growth factor (VEGF)-A and VEGF-C, but lower expression levels of VEGF-D and Prox-1 (all P < 0.001).
  
  
  CONCLUSIONS
  Our results show that there is only limited ongoing lymphangiogenesis in ccRCC. Given that several growth factors stimulate both angiogenesis and lymphangiogenesis, our observation indirectly indicates that haemangiogenesis predominates in ccRCC. This finding might provide better understanding of why ccRCCs prefer haematogenous dissemination to lymphatic spread.
authors.affiliation: Department of Pathology, GROW-School for Oncology and Developmental Biology, Maastricht University, Maastricht, the Netherlands. mbald@lpat.azm.nl
authors.forename: Marcella M
authors.initials: MM
authors.lastname: Baldewijns
authors.forename: Tania
authors.initials: T
authors.lastname: Roskams
authors.forename: Vera
authors.initials: V
authors.lastname: Ballet
authors.forename: Gert G
authors.initials: GG
authors.lastname: Van den Eynden
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Van Laere
authors.forename: Ilse
authors.initials: I
authors.lastname: Van der Auwera
authors.forename: Evelyne
authors.initials: E
authors.lastname: Lerut
authors.forename: Adriaan P
authors.initials: AP
authors.lastname: De Bruïne
authors.forename: Victor L
authors.initials: VL
authors.lastname: Thijssen
authors.forename: Peter B
authors.initials: PB
authors.lastname: Vermeulen
authors.forename: Hein
authors.initials: H
authors.lastname: van Poppel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000556:secondary*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000473:pathology*; D008198:Lymph Nodes / Q000473:pathology*; D042583:Lymphangiogenesis / Q000502:physiology*; D008207:Lymphatic Metastasis; D042601:Lymphatic Vessels / Q000473:pathology*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D040321:Vascular Endothelial Growth Factor Receptor-3 / Q000378:metabolism; D042442:Vascular Endothelial Growth Factors / Q000378:metabolism; D055815:Young Adult; D000098853:Podoplanin
chemical_list: D008562:Membrane Glycoproteins; D040321:Vascular Endothelial Growth Factor Receptor-3; D042442:Vascular Endothelial Growth Factors; C117468:PDPN protein, human; D000098853:Podoplanin