To assess 1)-whether nuclear β-catenin is a marker of endometrial precancer, and 2)-the diagnostic accuracy of β-catenin immunohistochemistry in the differential diagnosis between benign and premalignant endometrial hyperplasia (EH), defining criteria for its use.Electronic databases were searched for studies evaluating β-catenin immunohistochemistry in normal endometrium (NE), benign and/or premalignant EH and endometrioid carcinoma (EC). Odds ratio (OR;p<0.05), sensitivity, specificity, diagnostic-OR (DOR), positive and negative likelihood ratios (LR+, LR-) were calculated. Subgroup analyses were based on the classification system used (WHO or EIN) and criteria to define aberrant β-catenin expression (only nuclear or cytoplasmic/nuclear).Twelve studies with 1510 specimens were included. Nuclear β-catenin rate significantly increased from benign EH to NE (OR=26.01;p=0.0002, only in WHO subgroup), and from premalignant EH to benign EH (OR=3.89;p=0.0002; more markedly in EIN subgroup), but not from premalignant EH to EC (OR=0.78;p=0.29). Nuclear β-catenin accuracy was very low in WHO subgroup (sensitivity=0.40,specificity=0.76,LR+=1.85,LR-=0.72;DOR=2.89) and moderate in EIN subgroup (sensitivity=0.19,specificity=1.00,LR+=14.80,LR-=0.83;DOR=18.14). Cytoplasmic/nuclear β-catenin accuracy was absent in WHO subgroup (sensitivity=0.45,specificity=0.54,LR+=1.01,LR-=1.01;DOR=0.99) and low in EIN subgroup (sensitivity=0.57,specificity=0.86,LR+=3.63,LR-=0.51;DOR=8.30).Considering nuclear expression and using EIN system, β-catenin immunohistochemistry might be reliable as rule-in test for diagnosis of endometrial precancer, with perfect specificity and moderate overall accuracy. This article is protected by copyright. All rights reserved.