Postmenopausal osseous metaplasia of the endometrium: An uncommon histopathological entity: A case report.

Endometrial osseous metaplasia is a rare histopathological condition characterized by the presence of ectopic bone tissue within the endometrium. Although most commonly reported in women of reproductive age presenting with secondary infertility and menstrual abnormalities, it may occasionally occur in asymptomatic postmenopausal women. A 55-year-old postmenopausal woman with a history of invasive ductal breast carcinoma treated with surgery, radiotherapy, chemotherapy and 10 years of tamoxifen therapy was referred for evaluation of incidentally detected endometrial thickening (12 mm) on routine ultrasonography. Transvaginal ultrasound demonstrated a suspected endometrial polyp with posterior acoustic shadowing. Diagnostic hysteroscopy revealed osseous tissue and bone marrow within the endometrial cavity, raising concern for carcinosarcoma or another mesenchymal malignancy. Following multidisciplinary tumour board discussion, operative hysteroscopy with resectoscopy was performed, confirming the presence of osseous tissue; however, malignancy could not be definitively excluded. The patient subsequently underwent total hysterectomy with bilateral salpingo-oophorectomy. Final histopathological examination demonstrated atrophic endometrium containing two microscopic foci of bony tissue with degenerative and necrotic changes, confirming endometrial osseous metaplasia without evidence of malignancy. Notably, the patient had undergone pharmacologically induced abortion followed by dilation and curettage 35 years before diagnosis, suggesting that retained foetal bone fragments or trauma-induced metaplastic transformation may persist for decades and remain clinically silent before being detected incidentally. The present case highlights the importance of considering endometrial osseous metaplasia in the differential diagnosis of hyperechoic endometrial lesions, particularly in women with a history of pregnancy termination or uterine instrumentation. Transvaginal ultrasonography is a useful initial diagnostic modality, whereas hysteroscopy remains the gold standard for both diagnosis and treatment. Integration of clinical history, imaging findings and histopathological examination is essential to exclude malignancy and guide appropriate management.