Mature teratoma arising from intra-abdominal contralateral undescended testis in an infant: a case report.

A 4-month-old male infant was seen because of an asymptomatic undescended left testis and a right sided abdominal mass. CT revealed a calcified retroperitoneal tumour. Histological examination of surgical specimens showed a mature primary teratoma of the contralateral undescended testis. While this is very rare, infants with undescended testis should be carefully examined to rule out intra-abdominal malignant tumours.