A 38-year-old nulligravid woman presents to the office with a painful umbilical mass present for one year. She describes near daily pain, worse just prior to and during menses. She also reports a one- to two-year history of dysmenorrhea and intermittent dyspareunia. Currently her pain is 3 out of 10, and during menses it increases to 6 out of 10. Menses occur at 24-day intervals with up to 7 days of bleeding, heavy on days 1 to 3. She is not currently sexually active and has no history of sexually transmitted infections. She denies any past medical or surgical history. Her medications include a combination oral contraceptive pill and ibuprofen as needed for pain. She has no known drug allergies. Family history is unremarkable.