For this retrospective study, we collected cases of pregnancy complicated by adnexal masses treated at the Obstetrics and Gynecology Hospital of Fudan University (Shanghai, China) between January, 2010 and January, 2014. All the patients had undergone imaging using a transabdominal 13-MHz probe and we selected a total of 4 cases with benign pelvic masses initially misdiagnosed as ovarian cancer. This study was approved by the Obstetrics and Gynecology Hospital of Fudan University Institutional Review Board (Shanghai, China).

The patient was admitted at 23 weeks of gestation for a heterogeneous adnexal mass, sized 8×7×6 cm, which was discovered incidentally. Sonographically, there was a predominantly solid lesion with a middle hypoechoic area on the left adnexa, appearing to originate from the left ovary. Color Doppler evaluation (MyLab 90 Systems; Esaote S.p.A., Genova, Italy) demonstrated abundant arterial and venous flow (Fig. 1). We detected an accumulation of 1,000 ml of ascitic fluid. The fetus and the contralateral adnexa were normal in appearance. The mass was diagnosed as malignant left ovarian tumor on ultrasound. The carbohydrate antigen (CA) 125 levels were increased to 2,443.1 U/ml (normal, <35 U/ml). During laparoscopy a highly vascularized mass was identified at the periphery of the left ovary. There was a 800-ml blood loss and the patient received a transfusion intraoperatively (Fig. 2). The mass was diagnosed as luteoma of pregnancy on frozen section analysis. However, on postoperative pathological examination, the mass was definitively diagnosed as a theca cell tumor with luteinization. The follow-up of the pregnancy course was unremarkable and the patient delivered a 3,200-g infant at 39 weeks.

The patient was admitted at the 16th week of gestation, with persistent mild lower abdominal pain. She had undergone in vitro fertilization and embryo transfer and laparoscopic right salpingostomy for ectopic pregnancy with a uterine pregnancy at the 9th week. A transvaginal ultrasound indicated the presence of an inhomogeneous, predominantly solid lesion, sized 58×56×47 mm, on the left side of the uterus. Doppler ultrasound revealed a blood vessel encircling the mass. The ovaries were of normal morphology and size, with a normal double uterine pregnancy. The ultrasound diagnosis was fallopian tube cancer. The patient exhibited increased CA125 levels (256.1 U/ml). However, on laparoscopy, we observed an obsolete ectopic pregnancy in the left fallopian tube and salpingectomy was performed. The patient underwent a caesarean section at the 34th week of gestation as a result of pregnancy-induced hypertension syndrome and the birth weight of the infants was 2,200 and 2,450 g.

The patient was admitted during the 20th week of gestation, asymptomatic. Ultrasonography revealed a left-sided 18×16×15-cm adnexal mass, with a heterogeneous echo. The patient had increased CA125 (532.75 U/ml) and CA199 (13.87 U/ml) levels. The fetus and the contralateral adnexa appeared to be normal. The mass was diagnosed as ovarian cancer. A left adnexectomy was performed by laparotomy. Frozen section examination revealed a mature teratoma with abundant nervous tissue, which was pathologically confirmed postoperatively. The patient delivered by cesarean laparotomy at 40 weeks and the infant's weight was 3,250 g.

The patient was admitted during the 22th week of gestation, asymptomatic. A 15-cm adnexal mixed-echo mass was detected attached to the uterine wall. On Doppler examination, the mass exhibited abundant blood flow and a tangled bloodstream, and was diagnosed as right ovarian cancer. The patient had elevated CA125 levels (872.7 U/ml). However, the patient refused surgery; she underwent caesarean section at the 39th week and the birth weight of the infant was 3,050 g. Intraoperatively, a 16-cm mass arising from the uterine isthmus was identified, surrounded by dilated blood vessels; the mass was not excised. Both ovaries and fallopian tubes were of normal appearance. After 1 year, the patient was readmitted for the uterine mass. Laparoscopy was performed and a uterine myoma with degeneration was pathologically confirmed.