A mesothelial-lined cyst: an unusual presentation.

A 12-year-old girl presented with a "threadlike fiber" in her underwear associated with lower abdominal pain. She denied insertion of any foreign body, and at examination under anesthetic, a threadlike substance was seen exiting her external cervical os. Her only medical history was of an open appendicectomy for perforated appendicitis. Subsequent pathologic examination showed a collapsed mesothelial cyst, and laparoscopy showed a cyst and inflammatory changes consistent with previous appendicectomy surrounding her right ovary. We review the possible causes for this most unusual presentation.