Using flow cytometric analysis, Friel et al. 7 reported that the percentage of CD133+ cells in primary human endometrioid endometrial carcinoma samples ranged from 5.7% to 27.4% and also showed that CD133+ cells had greater tumour-initiating capacity relative to their CD133− counterparts. The gene discussed is PROM1; the disease is endometrial endometrioid carcinoma.