INTRODUCTION: Endometriosis is a common gynecological disease that affects approximately 10% of reproductive-age women. Inguinal endometriosis is uncommon, affecting only 0.6% of all patients with endometriosis. We present a case of inguinal endometriosis with a disappearing mass preoperatively. PRESENTATION OF CASE: A 44-year-old woman presented with a palpable mass and pain in her left inguinal region. Computed tomography showed a 20-mm mass near the pubic tubercle. After 2 months of observation, the mass became impalpable and could not be confirmed by computed tomography; however, the inguinal pain did not improve regardless of menstrual cycles. Resection of the inguinal mass and the entire extraperitoneal portion of the uterine round ligament was performed. Histopathological examination revealed endometrial glands and stroma with CD10-positive cells, which confirmed inguinal endometriosis diagnosis. Erythrophagocytic macrophages indicated endometriosis-related hematoma absorption. Her symptoms disappeared after surgery, and no postoperative complications occurred. DISCUSSION: For treating inguinal endometriosis, the complete removal of the mass and the entire extraperitoneal portion of the round ligament by an anterior approach is necessary to prevent postoperative residual symptoms and recurrence. However, the preoperative diagnosis of inguinal endometriosis remains a challenge and is frequently discovered incidentally by intraoperative findings and pathological examination. CONCLUSION: Clinicians should have a high suspicion of inguinal endometriosis and improved diagnostic precision to select the appropriate surgical approach. Regardless of menstrual variability, the feature of a decreased mass size caused by endometriosis-related hematoma absorption can serve as a preoperative diagnostic clue.
Inguinal endometriosis with a disappearing mass preoperatively: A case report