A 47-year-old G4P3013 female presented for IUD insertion. Transvaginal ultrasound was obtained secondary to difficult IUD placement. Ultrasound revealed a 9 cm left complex adnexal mass with IUD within the endometrial cavity. The serum OVA-1 test score was reported within normal limits for a premenopausal female. Pelvic MRI with contrast was obtained and revealed a large complex left adnexal mass with cystic components. The patient consented for a diagnostic laparoscopy with resection of the pelvic mass, bilateral salpingectomy, possible oophorectomy, laparotomy, and any other indicated procedures. Intraoperative findings revealed normal-appearing bilateral adnexa and a large left-sided pelvic retroperitoneal mass. Diagnostic laparoscopy with pelvic washings, resection of retroperitoneal pelvic mass, and bilateral salpingectomy was performed. Once the retroperitoneal entry was performed, a combination of blunt and electrocautery dissection was performed in order to mobilize the mass. The key retroperitoneal structures along the pelvic sidewall, including external iliac vessels and the ureter, were identified.