Among these, four genes (BUB1, CCNE2, MAD2L1, ORC6L) have been previously associated with poor-prognosis ER-positive breast cancers in a well-established 70-gene prognostic signature [58]; these genes are therefore probably important contributors to the more aggressive tumor characteristics of ER-positive breast cancers arising in younger patients. Here, MAD2L1 is linked to neoplasm.