PTEN immunohistochemistry in endometrial hyperplasia: which are the optimal criteria for the diagnosis of precancer?

Guidelines recommend protein phosphatase and tensin homolog (PTEN) immunohistochemistry for differentiating between benign endometrial hyperplasia (BEH) and atypical endometrial hyperplasia/endometrioid intraepithelial neoplasia (AEH/EIN). However, it is unclear when PTEN expression should be defined as 'lost' and thus suggestive of AEH/EIN. We aimed to determine the optimal immunohistochemical criteria to define PTEN loss in endometrial hyperplasia, through a systematic review and meta-analysis of diagnostic accuracy. Electronic databases were searched for studies assessing immunohistochemical expression of PTEN in both BEH and AEH/EIN specimens. PTEN status ('loss' or 'presence') was the index test; histological diagnosis ('AEH/EIN' or 'BEH') was the reference standard. Accuracy was quantified based on the area under the curve (AUC) on summary receiver operating characteristic (SROC) curves, for several different thresholds of PTEN expression. Eighteen studies with 1362 hyperplasias were included. Six different criteria to define PTEN loss were assessed. Low diagnostic accuracy was found for complete loss of expression (AUC = 0.71), presence of any null gland (AUC = 0.63), positive cells <10% (AUC = 0.64), positive cells <50% (AUC = 0.71) and moderate-to-null intensity (AUC = 0.64). Barely moderate diagnostic accuracy was only found for the subjective criterion 'weak-to-null intensity' (AUC = 0.78). Therefore, the clinical usefulness of PTEN immunohistochemistry in this field should be further investigated.