POLE-mutated atypical endometrial hyperplasia in an adolescent: a 5-year follow-up with LNG-IUS—a case report and literature review

This case report describes a rare instance of atypical endometrial hyperplasia (AEH) in a 16-year-old adolescent female presenting with secondary amenorrhea lasting 3 years. Imaging studies demonstrated a honeycomb-like intrauterine mass abutting the endometrial-myometrial junction, measuring 60 mm in length and 33 mm in maximal thickness. Diagnosis of POLE-mutated AEH (WHO 2020 criteria) was confirmed via hysteroscopic biopsy and molecular profiling. Initial treatment with oral megestrol acetate (160 mg/day) for 6 months failed to resolve complex hyperplasia, prompting a transition to a levonorgestrel-releasing intrauterine system (LNG-IUS). Over a 5-year follow-up period, endometrial thickness decreased from 17 mm to 6 mm, with histopathological confirmation of hyperplasia regression and no adverse effects on pubertal development or fertility. To our knowledge, this represents among the first documented cases of POLE-mutated AEH in an adolescent patient. The occurrence in a 16-year-old nulliparous female-lacking classic risk factors like obesity or PCOS-distinguishes this case from existing literature and highlights potential early-onset molecular pathogenesis. LNG-IUS achieved sustained remission after oral progestin failure, demonstrating 5-year efficacy and safety in this high-risk demographic. While POLE mutation analysis provided prognostic insights regarding disease behavior, it did not alter the fertility-preserving strategy, which adhered to guideline-based LNG-IUS therapy. Long-term follow-up supports LNG-IUS as a first-line option for adolescent AEH; molecular subtyping may refine risk stratification but requires validation before routine integration.