A Rare Case of Endometrial Ossifying Cartilaginous Metaplasia

Endometrial ossification, also described as endometrial osseous metaplasia (EOM), is a rare benign condition characterized by the presence of bone tissue within the endometrium. Its exact etiopathogenesis remains unclear, although the metaplasia of endometrial stromal cells into osteoblast-like cells has been proposed as the most accepted mechanism. Clinically, it may present with infertility, abnormal uterine bleeding, or pelvic discomfort and, in rare situations, may mimic more serious gynecological pathology. We report the case of a 60-year-old postmenopausal woman who presented with persistent vaginal bleeding, vaginal discharge, and a protruding vaginal mass causing discomfort. She had a long history of recurrent postmenopausal bleeding (PMB) and previously diagnosed benign endometrial polyps managed with hysteroscopic polypectomy. Imaging revealed a markedly thickened, inhomogeneous endometrium with multiple polypoidal lesions and calcifications, raising suspicion for endometrial malignancy with possible cervical involvement. Due to persistent symptoms, suspicious imaging findings, and the patient's multiple comorbidities, a robotic total hysterectomy with bilateral salpingo-oophorectomy was performed. Histopathological examination unexpectedly revealed the ossifying cartilaginous metaplasia of the endometrial stroma involving the endometrium and an endometrial polyp, with no evidence of malignancy. The patient had an uneventful recovery and remained asymptomatic on follow-up. This case highlights how a rare benign diagnosis can present in a complex clinical scenario mimicking malignancy. The awareness of such entities is important to avoid misdiagnosis and to emphasize the crucial role of histopathology and multidisciplinary management in achieving safe, patient-centered care.