CD9 and nonpapillary renal cell carcinoma: 22 chRCC showed strong CD9 expression and 2 showed weak expression out of a total of 24 whereas 4 ccRCC showed strong CD9 expression and 10 weak expression out of a total of 229 (p < 0.0001 for weak or strong positive staining in ccRCC versus chRCC by Fisher exact test).