Tumor types are classified using WHO grading based on histologic and functional features.

基于组织学和功能特征，肿瘤类型根据世界卫生组织标准分级。

The scale goes from I to IV based on the morphologic and functional features of the tumor cells; a grade IV tumor being the most abnormal looking cells that also tend to be the most aggressive.

基于肿瘤细胞的形态和功能特征，分为从I级到IV级；细胞形态最为异常的IV级肿瘤也往往最有侵袭性。