CD99 and neoplasm: Tumor cells from all 17 malignant kidney neoplasms studied showed expression of CD271+ and CD81hi, together with positivity for EpCAM in the majority (12/17) of tumors (70%) and CD90 in 5/17 (29%), while they systematically lacked CD57, CD58, CD99, CD117, nuMyoD1, and numyogenin expression (Figure 3 and Table S2).