<prompt> The most important prognostic factor of Wilms tumor -HistopathologyPloidy of cellsAge 1 yrMutation of c 1 p gene  <response>: Anaplastic nuclear change is the only criterion of unfavourable histology in Wilms tumor and all Wilms tumor lacking this feature are designated as having favourable histology.Anaplastic nuclear change reflects extreme polypoidy is usually apparent under low magnification. Anaplastic histology remains a critical determinant of adverse prognosis. Even anaplasia restricted to kidney confers an increased risk of recurrence death, underscoring the need for correctly identifying this histologic features. Robbins 8the pg 481 