CD44 and cancer: Although unique variants were observed in the EPCAM+CD44+CD49f+ cells, these may correspond to a quiescent subpopulation of cancer initiating cells or represent de novo acquired mutations that have yet to populate the bulk tumor, as enrichment of the EPCAM+CD44+CD49f+ subpopulation may have uncovered variants that could be present in low frequency in the bulk tumor, but at higher frequency with respect to the cancer initiating cell subpopulation.