Anti-PTEN mAb suitable to detect by IHC the expression of PTEN in tumor tissues were generated and described soon after the discovery of PTEN as a major tumor suppressor.56,57 Significant efforts have been made since then to technically optimize, validate, and standardize the available anti-PTEN mAb for their IHC reliable use in research and diagnosis.58–70 However, precision studies aiming to define the topological and molecular properties of the epitopes recognized by these anti-PTEN mAb, which is substantial to understand their immunostaining patterns, are still lacking. This evidence concerns the gene PTEN and neoplasm.