A low frequency of lymph node metastasis in clear‐cell renal cell carcinoma is related to low lymphangiogenic activity

OBJECTIVE To assess ongoing lymphangiogenesis in renal cell carcinoma (RCC) by histomorphometry and by quantifying mRNA expression levels of lymphangiogenesis‐related factors. MATERIALS AND 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