Metaplasia, Dysplasia and Anaplasia.

Metaplasia (Greek: "change in form") is the reversible replacement of one differentiated cell type with another mature differentiated cell type.

Dysplasia (from the Greek δυσπλασία "malformation", δυσ- "mal-" + πλάθω "to create, to form"), is a term used in pathology to refer to an abnormality of development.[1] This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells.

Anaplasia refers to a reversion of differentiation in cells and is characteristic of malignant neoplasms (tumors). Sometimes, the term also includes an increased capacity for multiplication. Lack of differentiation is considered a hallmark of malignancy.