CD44 and breast neoplasm: Independent of the cell of origin (E or M clones, or freshly sorted E and M cells) the vast majority (65%-95%) of cells growing in suspension as mammospheres were CD24-/CD44+(M) cells (Fig 3C and S4 Fig), while cells in the CD24+/CD44-(E) state were usually not detected as has also been observed in primary breast tumor cells [42].