Increased Vitamin D Receptor Immunoreactivity in Endometrial Polyps: An Exploratory Single-Center Pilot Study

This study aimed to compare vitamin D receptor (VDR) immunoexpression in endometrial polyps and paired adjacent normal endometrium.

Seventeen women (mean age, 48 ± 9 years) undergoing hysteroscopic polypectomy were included. Paired samples of polyp tissue and adjacent normal endometrium were analyzed by standardized immunohistochemistry using an anti-VDR monoclonal antibody. Two blinded pathologists independently assessed staining intensity (0-3) and fraction of positive cells (0-2), and calculated a composite van Slooten score (0-6). VDR positivity was defined as a composite score ≥ 3.

VDR expression was higher in polyps than in normal endometrium. Mean intensity (1.5 ± 1.1 vs. 0.8 ± 0.8; p = 0.041), fraction of stained cells (1.1 ± 0.7 vs. 0.4 ± 0.7; p = 0.020), and composite score (2.6 ± 2.0 vs. 1.0 ± 1.5; p = 0.020) were significantly greater in polyps. VDR positivity was observed in 58.8% (10/17) of polyps and 23.5% (4/17) of normal endometrial samples (p = 0.037). Interobserver agreement was substantial to almost perfect (κ = 0.70-0.85). No association was observed between VDR score and age, BMI, or menopausal status.

Endometrial polyps exhibit increased VDR expression compared with paired normal endometrium. These exploratory findings suggest compensatory VDR upregulation in benign proliferative lesions, warranting confirmation in larger molecular studies.