Pediatric cystic nephromas (previously multilocular cystic nephromas) are a type of cystic renal lesion in children occurring most frequently in patients between the ages of 3 months and 4 years old. 

The above case represents a typical lesion. Particularly, herniation into the renal pelvis is a common finding which can be seen in this case (in the Axial cross sections, Key Image has been set to an image reflecting cyst herniation into the renal pelvis), and confirmed at histology.