Review Question - QID 215103

A 24-year-old G1P1 woman presents to clinic with intermittent right lower quadrant abdominal pain over the past 2 months. The pain is sharp, lasts for a few minutes, and always goes away. Acetaminophen provides no relief. The pain is not associated with her menstrual cycle or intercourse. The patient’s last menstrual period was 3 weeks prior. Menses occurs regularly every 28 days and lasts about 4 days. She is sexually active and uses condoms for contraception. She has no remarkable past medical or surgical history. Family history is notable for an aunt who was diagnosed with ovarian cancer at the age of 66. Her temperature is 98.5°F (36.9°C), blood pressure is 128/84 mmHg, pulse is 82/min, and respirations are 14/min. Pelvic exam reveals a right adnexal mass. There is no evidence of cervical or vaginal bleeding. Urine beta-hCG is negative. A pelvic ultrasound reveals a 5-cm complex cystic mass with calcified components and thick sebaceous fluid in the right ovary. Which of the following is the most likely diagnosis?