Case reportA 39 year old nulliparous woman was referred to the outpatient department by her general practitioner following the detection of an abdominal swelling, found incidentally during a routine visit to obtain a cervical smear for cytology. She had no other medical complaints and had not noted any pressure symptoms or systemic disturbance in association with the mass. The previous cervical smears had been normal.She had regular menstrual periods, bleeding for five days in a 28 day cycle. There had been no associated bleeding irregularity, pain or significant weight loss. She was not sexually active and therefore did not use any contraceptives, although she had had an intrauterine contraceptive device inserted for one year, 12 years previously.This was removed following an episode of severe pelvic pain. A left ovarian cyst had also been diagnosed 18 years prior to this referral. The cyst appeared to have resolved spontaneously and no further treatment had been required. She smoked about 20 cigarettes per day and suffered from mild chronic bronchitis. In addition, she was receiving treatment for left lower limb sciatica.General physical findings were normal at presentation. There was no sign of pallor, lymphadenopathy, respiratory or cardiovascular disease. Further examination revealed a nontender, smooth, cystic mass arising from the pelvis which was consistent in size with an 18-week pregnancy. There was no other palpably enlarged organ, no clinical evidence of ascites, and no bruit were heard over the mass. Pelvic examination revealed a mobile, normal sized uterus, separate from, and anterior to the mass.Laboratory investigations performed subsequently were all reported normal. These included estimation of the serum CA125, alpha fetoprotein, carcinoembryonic antigen, human chorionic gonadotrophin and serum carbohydrate antigen C19-9. A full blood count, kidney