ALDH1A1 and neoplasm: Figure 11C shows ALDH1 positive cells infiltrating a lymphatic vessel, while surrounding tumour cells are ALDH1-negative. CD133+ cells were stained in xenograft tissue slices at the apical membrane of ductal epithelial cells. Intracellular expression was detected in some cells. Cellular debris within the ductal lumen was strongly stained with CD133/1 (AC133) antibody. We could not detect CD133 in the primary tumour tissue (Fig. 11).