Review Question - QID 214942

A 28-year-old nulliparous woman presents to clinic reporting a 4-month history of right-sided pelvic pain. It is exacerbated during sexual intercourse. She has similar pain with defecation. She was treated for chlamydia with appropriate antibiotics 6 weeks ago. Her last menstrual period was 10 days ago. Her menstrual cycles are regular, occurring every 28 days with 5 days of moderate bleeding. She has no other medical history and takes no medications. The patient does not use tobacco, alcohol, or illicit drugs. Her temperature is 99.5°F (37.7°C), blood pressure is 110/60 mmHg, pulse is 80/min, and respirations are 16/min. Examination reveals a small, retroverted uterus with cervical motion tenderness. Transvaginal ultrasound reveals a homogenous, cystic mass on the right ovary. Which of the following is the most likely diagnosis?