Stage and Pathology
Clinical stage was based on COG staging system. Initial pathology was
according to the COG protocol and classified into favorable histology
(FH) group and unfavorable histology (UFH) group. The FH group were
classified into four subtypes: mesenchymal, epithelial, blastemal
predominant, and mixed. The UFH group included diffuse anaplasia and
focal anaplasia.