Abstract
BACKGROUND: Endometriosis is a common benign gynecological disease that causes dysmenorrhea in women of childbearing age. Malignant tumors derived from endometriosis are rarely reported and are found in only 1% of all patients with endometriosis. Here, we report a well-differentiated squamous cell carcinoma (SCC) caused by squamous metaplasia of endometriosis that co-occurred in the uterus and ovaries. CASE SUMMARY: A 57-year-old postmenopausal woman had a 6-month history of irregular uterine bleeding. The uterus and adnexa were examined by computed tomography, and there were two solid cystic masses in the pelvis and right adnexa. Histological findings of surgical specimens showed well-differentiated SCC arising from squamous metaplasia of ectopic endometrial glands in the uterus and ovaries. The patient received chemotherapy after surgery and was followed up for 3 mo without metastasis. CONCLUSION: The continuity between ectopic endometrial glands and SCC supports that SCC originates from ectopic endometrial glands with metaplasia towards squamous epithelium.