Highly pleomorphic and bizarre cytologic features associated with malignant tumors that are poorly differentiated.


A condition of cells with poor cellular differentiation, losing the morphological characteristics of mature cells and their orientation with respect to each other and to endothelial cells.

The term also refers to a group of morphological changes in a cell including nuclear pleomorphism, altered nuclear-cytoplasmic ratio, presence of nucleoli, high proliferation index, that point to a possible malignant transformation.

Such loss of structural differentiation is especially seen in most malignant neoplasms.

The term also includes an increased capacity for multiplication.

Lack of differentiation is considered a hallmark of aggressive malignancies.

Some cancers arise from stem cells in tissues, and failure of differentiation, rather than dedifferentiation of specialized cells, account for undifferentiated tumors.

Anaplastic cells display marked pleomorphism.

The nuclei are characteristically extremely hyperchromatic and large.

The nuclear-cytoplasmic ratio may approach 1:1 instead of the normal 1:4 or 1:6.

Anaplastic nuclei are variable and bizarre in size and shape.

The chromatin is coarse and clumped.

The nucleoli may be large in size.

More important, mitoses are often numerous and distinctly atypical.

Anaplastic cells usually fail to develop recognizable patterns of orientation to one another.

Anaplastic cells may grow in sheets, with total loss of communal structures, such as gland formation or stratified squamous architecture.

It is the most extreme disturbance in cell growth encountered in the spectrum of cellular proliferations.

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