Deep infiltrating endometriosis presenting as acute abdomen with extremely elevated tumor markers: a cancer-mimicking case

BACKGROUND: Deep infiltrating endometriosis (DIE) is a rare and severe subtype of endometriosis that can cause marked distortion of pelvic anatomy. Diagnosis becomes particularly challenging when it presents as an acute abdomen with significantly elevated tumor marker levels. In this study, we describe a rare and deceptive presentation of acute abdomen caused by severe DIE that closely mimicked ovarian carcinoma. CASE PRESENTATION: A 42-year-old woman (gravida 1, para 1) was admitted with sudden-onset severe diffuse abdominal pain lasting 5 hours. Preoperative findings-including cancer antigen 125 and carbohydrate antigen 19-9 were both elevated to approximately 20-fold above the upper limit of normal, along with imaging results-strongly suggested a ruptured malignant ovarian tumor. Intraoperatively, the lesions were indistinguishable from advanced ovarian cancer, and a definitive diagnosis of deep infiltrating endometriosis (American Society for Reproductive Medicine score 178, Stage IV) was confirmed only through postoperative histopathological examination. Her postoperative recovery was unremarkable, with rapid symptomatic relief, and no recurrence was observed during follow-up. CONCLUSION(S): This case highlights that deep infiltrating endometriosis should be considered in patients presenting with acute abdomen, even when clinical and biochemical features strongly suggest pelvic malignancy. Furthermore, the emergency surgery for definitive diagnosis and radical resection also achieved excellent therapeutic outcomes.