What describes anaplasia in terms of cellular differentiation?

Anaplasia refers to the loss of differentiation and the reversion of cells to a more primitive or less specialized state. In the context of tumor classification, when cells undergo anaplasia, they may become unrecognizable in terms of the structure and function when compared to normal, mature tissues or parenchyma. This characteristic is indicative of malignancy, as anaplastic cells often exhibit significant variability in size and shape (pleomorphism), abnormal nuclear features, and a lack of organization, making them distinctly different from the normal cells of the tissue of origin.

This unrecognizability is crucial as it reflects a high degree of cellular alteration associated with aggressive tumor behavior. In malignant neoplasms, the more anaplastic a cell is, the more it typically correlates with aggressive disease and worse prognosis. Hence, the defining trait of anaplasia is its stark deviation from normal cellular characteristics, corroborating that these cells no longer bear semblance to their original differentiated counterparts.