Malignant Transformation of Ovarian Endometrioma During Long-Term Dienogest Therapy: A Case Report

Dienogest, a novel progestin, is considered an effective pharmacological intervention for ovarian endometrioma due to its favorable side effect profile. We present a rare case of malignant transformation of an ovarian endometrioma into carcinoma following long-term (exceeding 10 years) hormonal management with dienogest. The patient, a 54-year-old Japanese woman, had initially been advised to undergo surgical management at age 42 due to suspected deep infiltrating endometriosis. Preferring a conservative approach, she sought symptomatic relief through hormonal therapy at our institution.