Elevated Risk of Endometrial Cancer and Precursor Lesions in Patients With Myotonic Dystrophy: A Retrospective Study at a Single Institution in Japan

AIM: Myotonic dystrophy (MD) has been associated with an increased risk of endometrial cancer (EC) in Western countries; however, data from Japan are limited. This study aimed to evaluate the incidence and clinical characteristics of EC and its precursor lesion, atypical endometrial hyperplasia (AEH), in Japanese patients with MD. METHODS: We retrospectively reviewed medical records of female patients with MD (MD group, n = 36) and those with other types of muscular dystrophy (control group, n = 84) treated at a single institution between 2008 and 2023. RESULTS: EC/AEH was identified in 5 of 36 patients in the MD group (13.9%), including 3 cases of EC and 2 of AEH, whereas 1 case of EC (1.2%) was observed among 84 control patients, indicating a significantly higher incidence in the MD group (p = 0.014). The median age at diagnosis of EC/AEH in the MD group was 45 years, which was significantly younger than that of non-MD EC/AEH cases treated during the same period (median 59 years). All surgically treated EC cases were early-stage endometrioid carcinoma and achieved favorable oncological outcomes, although perioperative respiratory complications were observed. CONCLUSIONS: Japanese MD patients have a significantly higher risk of developing EC/AEH at a younger age compared with non-MD patients. These findings highlight the importance of regular gynecological surveillance in women with MD.