PECAM1 and neoplasm: We propose that these MECA32-negative cells are tumor-derived because they are positive for the human chromosome 17 and HER-2 (Figure 2 D), are positive for the Y-chromosome and CD31 in xenotransplantations of male melanoma patient cell lines in female mice (Figure 2 G), are positive for the ALU-repeat and CD31 (Figure 3 A–D) and they express transfected green fluorescent protein (Figure 2 I, J).