Recent studies indicate that ER/PR/HER-2-negative (triple-negative, TN) breast cancers may be "CTA-rich" tumors, suggesting the possibility of CTA-based cancer vaccines as a treatment option for patients bearing these tumors. MAGE-A10 together with NY-ESO-1 is probably the most immunogenic CTA, representing a potentially highly attractive target of active specific immunotherapies. Paraffin-embedded tumor sections were collected retrospectively from 165 breast cancer patients diagnosed between 2002 and 2003. Immunohistochemical staining for MAGE-A10 and NY-ESO-1 was performed. The expression of MAGE-A10 and NY-ESO-1 was correlated with other clinicopathological variables. MAGE-A10 expression (score ≥ 2+) was detected in 105/164 (64%), and NY-ESO-1 expression (score ≥ 2+) was observed in 14/164 (8.5%) patients. No correlation between MAGE-A10 and NY-ESO-1 expression and tumor size, tumor grade, Ki-67 and lymph nodes status was detectable. MAGE-A10 expression was significantly associated with ER-negative (P = 0.002), PR-negative (P = 0.002) and HER-2-negative (P = 0.044) tumors. We clearly showed that MAGE-A10 is frequently expressed in the group of TN patients, where the majority (85.7%) of tumors express this CTA. Because of limited therapeutic options for the triple-negative breast cancer, the frequent expression of MAGE-A10 CTA in these cancers may offer the opportunity for a much needed additional treatment for this group of patients.