β‑catenin expression in endometrioid type endometrial cancer: Expression patterns and impact on disease outcomes

Abstract

Determination of nuclear and/or cytoplasmic expression of β‑catenin by immunohistochemistry in patients with endometrial cancer (EC) may constitute a potential diagnostic method for identifying patients with a catenin β1 (CTNNB1) gene mutation and those at risk of disease recurrence. The present study aimed to investigate β‑catenin expression patterns in hysterectomy specimens of patients with endometrioid type EC using immunohistochemistry, and to examine the prognostic impact of β‑catenin. The study was a single‑institutional, retrospective cohort trial enrolling consecutive patients with a postoperative histopathological diagnosis of endometrioid EC who underwent hysterectomy between January 2015 and December 2018. Histopathology slides from 75 patients were stained with a monoclonal antibody targeting the β‑catenin protein. Any percentage of nuclear staining, whether focal or diffuse, was considered ‘β‑catenin nuclear‑positive’. The cytoplasmic staining reaction of β‑catenin was assessed based on the percentage of stained cells and staining intensity. Immune‑reactivity score (IRS) values were determined by multiplying the scores for the percentage of staining and staining intensity. IRS values 0 to 2 were regarded as negative expression, 3 to 4 as low expression, 6 to 8 as moderate expression, and 9 to 12 as high expression. Recurrence‑free survival (RFS) was used as the prognostic endpoint. Only 2 out of 75 tissue samples (2.7%) exhibited nuclear β‑catenin expression, with a low staining percentage of 5%. By contrast, cytoplasmic staining was observed in all samples (100%). According to the IRS findings, 1.3% of the samples exhibited negative cytoplasmic expression, 42.7%