<prompt> The most impoant prognostic factor of Wilms tumor-HistopathologyPloidy of cellsAge 1 yMutation of c 1p gene  <response>: Robbins basic pathology 10th edition page no 290. Wilms tumor or nephroblastoma is the most common primary tumor of the kidney in children. On microscopic examination, Wilms tumors are characterized by recognizable attempts to recapitulate different stages of nephrogenesis. The pattern of anaplastic cells within the primary tumor has impoant implications for prognosis. 