[Primitive neuroectodermal tumor of the kidney in children; its differential diagnosis with Wilms tumor].

There may be a number of tumors made up by small round blue cells in the kidneys of children. One of them is primitive neuroectodermal tumor (PNET). The differences in therapeutic approaches determine the need to establish an accurate diagnosis. The differential diagnosis of PNET and the blastemal component of Wilms tumor can be difficult due to the similar histological pattern. There is a need for a close analysis of morphological manifestations, by keeping in mind the age of patients, and supplementary studies. A strong CD99 membrane expression and nuclear FLI1 expression in tumor cells are the signs of PNET. Reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization can determine PNET-specific translocations [t(11;22)(q24;q12), by involving the EWS gene.