PTEN and breast cancer: Notably, Stern et al., reported that HER2+ BC patients treated with chemotherapy with or without Trastuzumab in the context of the adjuvant phase III BCIRG 006 trial who lacked PTEN expression exhibited poorer disease-free survival (DFS) and overall survival (OS), as compared to those with detectable PTEN staining by immunohistochemistry [33].