Prognostic significance of microscopic vascularity for clear cell renal cell carcinoma

To investigate the association between tumour vascularity and patient survival in a series of clear-cell renal cell carcinoma (RCC), which often metastasizes via the vascular route and frequently has a prominent vascular network.

Vessels were labelled in sections from 150 cases of clear cell RCC by factor VIII immunohistochemistry. The mean microvessel density (MMD), expressed as the number of vessels per 10 high-power fields (HPFs, x400, aggregate field area 1.452 mm2) and tumour microvessel area (TMA), expressed as the percentage of the total tumour area within 10 HPFs, were measured for each case. The relationship between MMD and TMA, tumour stage and grade, and patient survival over a 5-year follow-up was determined.

Tumour MMD ranged from 1 to 238 vessels per HPF, while the TMA was 1.2-60.8%. There was a weak but significant difference for MMD between tumour grades (P < 0.01) and stages (P < 0.05). There was no significant association between TMA and either tumour stage or grade. Division of cases according to MMD < or = 40 and > 40 per HPF showed a significant difference in survival curves between both groups, with a higher MMD being associated with longer patient survival. The significant association between MMD and survival was retained for stage 3 tumours only when cases were stratified according to Robson's stage at presentation. TMA did not correlate with survival.

The assessment of tumour vascularity is of prognostic significance for clear cell RCC. The significant inverse relationship between MMD and patient survival suggests that for tumours with a poor prognosis, decreased MMD is associated with tumour fibrosis and the development of large diameter vascular channels.