Because more cells than expected in one of the healthy donors matched the putative CTC phenotype CD45-/(CK/β-cat)-/VIM+, and in previous CTC work significant numbers of cells harvested did not express any of the cancer cell markers in our panel [14, 15], we sought to improve CTC identification by supplementing the detection expressed VIM with a biomarker specific to sarcomas. This evidence concerns the gene PTPRC and cancer.