ERBB2 and breast carcinoma: To explore the clinical significance of PTEN status in predicting response to trastuzumab-based therapy, we evaluated PTEN expression in 17 HER2/neu-overexpressing primary breast carcinomas from patients who subsequently developed metastatic breast cancer and received trastuzumab plus paclitaxel therapy after preliminary evaluation, and in 20 other randomly selected breast cancer patients.