Background
PTEN is a tumor suppressor gene in signaling downstream of EGFT. Loss of PTEN protein expression is one of the more common occurrences in human cancers, and its loss potentially reduces the benefit from trastuzumab and EGFR-targeted therapies and mTOR inhibitors. Loss of PTEN is usually assessed with immunohistochemistry (IHC). Mutation analysis of PTEN gene has been recently introduced in clinical use. In this study, we compared the concordance between PTEN IHC and PTEN sequencing technologies using the largest cohort of patients published thus far.