The Collaborative International Dictionary of English v.0.48:

anaplasia \anaplasia\ n.
   1. loss of structural differentiation within a cell or group
      of cells often with increased capacity for multiplication,
      as in a malignant tumor.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

anaplasia
    n 1: loss of structural differentiation within a cell or group
         of cells often with increased capacity for multiplication,
         as in a malignant tumor