Prenatal ultrasonographic features of mature cystic teratoma in undescended testicle

A 31-year-old nulliparous woman with an uneventful pregnancy was referred to our center at 32 weeks' gestation following observation of a fetal intra-abdominal cystic mass on routine third-trimester ultrasound examination. The ultrasound examination revealed a single, unilocular, anechoic left abdominal cystic lesion with well-defined boundaries, measuring 20 × 20 × 22 mm and containing a scarcely vascularized small (6 × 3 mm) intracystic solid component (Figure 1a, c and d). The lesion was apparently retroperitoneal, located between the left kidney and the urinary bladder, separated from both and from the vertebral column. Careful examination of the scrotal sac using both two-dimensional (2D) and three-dimensional (3D) ultrasound revealed the presence of only one testicle (right) in the fetal scrotum and an absence of the left testicle (Figure 1b and Videoclip S1). A preliminary diagnosis of fetal testicular teratoma in an undescended testicle was made. Subsequent follow-up ultrasound examination at 35 weeks confirmed these findings and saw no change in cyst size.