Clinicopathological Significance of Claudin-6 Immunoreactivity in Low-grade, Early-stage Endometrioid Endometrial Carcinoma

Background/Aim: Dysregulation of claudin 6 (CLDN6) expression has been widely documented in various malignancies. CLDN6 is aberrantly expressed in many types of human carcinomas; however, its clinical significance in endometrial carcinoma has seldom been investigated. This study aimed to examine the immunohistochemical expression status of CLDN6 in low-grade, early-stage endometrioid endometrial carcinoma (LGES-EEC) and to assess its clinicopathological significance. Materials and Methods: We performed immuno-staining for CLDN6 in 118 tissue samples from LGES-EECs. Protein expression levels were interpreted using a semi-quantitative histoscore method. All statistical analyses were performed. Results: CLDN6 was primarily localized along the membranes of the tumor cells. We considered histoscore ≥10 (the staining proportion ≥5% and intensity ≥2) as positive immunoreactivity for CLDN6. Twenty-six of the 118 patients (22.0%) showed CLDN6 positivity. Positive CLDN6 expression was significantly associated with deeper myometrial invasion (p=0.001), higher initial stage (p=0.015), and substantial lymphovascular space invasion (p=0.018). Conclusion: Aberrant CLDN6 expression is involved in tumor progression in LGES-EECs. In addition, targeting CLDN6 may offer clinical utility in patients with endometrial carcinoma.