Background:　Proto-oncogene　MYC　has　been　indicated　to　promote　progression　of　many　cancers.　However,　prognostic　and　clinicopathological　significance　of　MYC　in　breast　cancer　need　further　evaluation.　Methods:　We　searched　EMBASE　and　PubMed　databases　to　find　useful　studies.　We　analyzed　relationships　between　high　MYC　expression　and　prognostic　data/　clinicopathological　features　through　hazard　ratio　(HR)　and　odds　ratio　(OR).　Each　statistical　test　was　two-sided.　Results:　There　were　29　studies　(36　cohorts)　with　12621　patients　enrolled　in　our　study　The　MYC　overexpression　was　associated　with　worse　DFS/RFS　(disease/relapse　free　survival)　in　11　studies　(16　cohorts)　with　5390　patients,　and　OS　(overall　survival)　of　7　studies　(8　cohorts)　with　2672　patients.　Subgroup　analysis　according　to　ethnicity/technique/data　source　displayed　that　MYC　overexpression　was　associated　with　poor　DFS/RFS　in　FISH,　other　technique,　all　data　source　and　Asian/Non-Asian　subgroup,　and　worse　OS　in　all　subgroups.　In　addition,　MYC　overexpression　was　related　to　large　tumor　size,　high　histologic　grade,　lymph　node　metastasis,　negative　hormone　receptors　and　positive　Ki67　expression.　Conclusions:　Our　results　showed　that　MYC　overexpression　was　associated　with　worse　prognosis　and　high　risk　of　breast　cancer,　especially　in　patients　with　negative　hormone　receptors,　which　highlighted　the　potential　of　MYC　as　a　significant　prognostic　biomarker　of　breast　cancer.