anaplasia

n. loss of structural differentiation of unique features inside a cell or group of cells; dedifferentiation

Anaplasia or de-differentiation refers to cells that are abnormally undifferentiated. The loss (or lack) of normal cell differentiation is characteristic of most very malignant tumors.
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Anaplasia /ana·pla·sia/ dedifferentiation ; loss of differentiation of cells and of their orientation to one another and to their axial framework [more]Anaplasia - Community and Resources

Noun
1. loss of structural differentiation within a cell or group of cells often with increased capacity for multiplication, as in a malignant tumor
(hypernym) dysplasia

noun
loss of a cell's characteristics, caused by cancer