Quantitative PCR showed that HOTAIR is overexpressed from hundreds to nearly two thousand- fold in breast cancer metastases, and HOTAIR level is sometimes high but heterogeneous among primary tumors . We next measured HOTAIR level in an independent panel of 132 primary breast tumors (stage I and II) with extensive clinical follow-up13. Indeed, nearly one third of primary breast tumors overexpress HOTAIR by over 125-fold over normal breast epithelia, the minimum level of HOTAIR overexpression observed in bona fide metastases, and high HOTAIR level is a significant predictor of subsequent metastasis and death.