We observed weak PTEN expression (− and 1+: IRS<7) in 40.0–49.1% of the tumours examined (eight out of 17 of the patients who received trastuzumab and paclitaxel, and eight out of 20 from the preliminary study), which is consistent with previous reports that ∼50% of breast cancers are PTEN deficient (Perren et al, 1999; Depowski et al, 2001). Here, PTEN is linked to neoplasm.