A 19-year-old woman presented to the emergency department with a 7-year history of periodic lower abdominal and pelvic pain without fever, chills, or dysuria. She had not had menses nor vaginal intercourse. Physical exam revealed lower abdominal distention and a firm and tender suprapubic mass extending from the pelvis to the umbilicus. A perineal exam is seen in the image.
What is the likely diagnosis?
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