Increased Expression of CD44s in Conventional Renal Cell Carcinomas with Renal Vein or Vena Cava Thrombosis

Objectives: CD44 is thought to play an important role in the tumorigenesis of renal cell carcinoma (RCC). We retrospectively evaluated the expression of CD44s by immunohistochemical analysis in conventional RCC patients and in conventional RCC patients with renal vein or vena cava thrombus and investigated the differences in the pattern of expression of CD44s between the two groups. Methods: Thirty RCC specimens and four RCC specimens with renal vein and five RCC specimens with vena cava thrombus were analyzed immunohistochemically using a CD44s-specific antibody. The expression of CD44s in RCC with renal vein or vena cava thrombus was compared with the expression of CD44s in RCC without renal vein or vena cava extention. Results: Of the 30 tumor specimens without thrombus, 16 (53%) expressed CD44s. Staining was also positive in all of the nine specimens with thrombus. CD44s expression was weak in the tumour specimens without thrombus. RCC specimens with renal vein or vena cava thrombus exhibited strong positive staining for CD44s. Conclusions: The increased expression of CD44s seems to be correlated with tumor thrombus formation in renal vein or vena cava. CD44s may play a role in the formation of renal vein or vena cava extention.