THY1 and neoplasm: CD90 expression is associated with primitive hematopoietic progenitor cells, normal mesenchymal stromal cells and tumor cells that have undergone the epithelial-to-mesenchymal transition,8–10 a process well implicated in cancer metastasis.11,12 This inclusive cell collection strategy was optimized for cell recovery, including cells expressing low levels of EpCAM and/or CD90.