Anaplasia
Encyclopedia
Anaplasia refers to a reversion of differentiation in cells and is characteristic of malignant neoplasms (tumor
s). Sometimes, the term also includes an increased capacity for multiplication. Lack of differentiation is considered a hallmark of aggressive malignancies. The term anaplasia literally means "to form backward". It implies dedifferentiation, or loss of structural and functional differentiation of normal cells. It is now known, however, that at least some cancers arise from stem cell
s in tissues
; in these tumors failure of differentiation, rather than dedifferentiation of specialized cells, account for undifferentiated tumor
s.
Anaplastic cells display marked pleomorphism
. The nuclei
are characteristically extremely hyperchromatic (darkly stained) and large. The nuclear-cytoplasmic ratio
may approach 1:1 instead of the normal 1:4 or 1:6. Giant cells that are considerably larger than their neighbors may be formed and possess either one enormous nucleus
or several nuclei (syncytia). Anaplastic nuclei are variable and bizarre in size and shape. The chromatin
is coarse and clumped, and nucleoli may be of astounding size. More important, mitoses are often numerous and distinctly atypical; anarchic multiple spindles may be seen and sometimes appear as tripolar or quadripolar forms. Also, anaplastic cells usually fail to develop recognizable patterns of orientation to one another (i.e. they lose normal polarity). They may grow in sheets, with total loss of communal structures, such as gland
formation or stratified squamous architecture. Anaplasia is the most extreme disturbance in cell growth encountered in the spectrum of cellular proliferations.
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s). Sometimes, the term also includes an increased capacity for multiplication. Lack of differentiation is considered a hallmark of aggressive malignancies. The term anaplasia literally means "to form backward". It implies dedifferentiation, or loss of structural and functional differentiation of normal cells. It is now known, however, that at least some cancers arise from stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s in tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
; in these tumors failure of differentiation, rather than dedifferentiation of specialized cells, account for undifferentiated tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s.
Anaplastic cells display marked pleomorphism
Pleomorphism (cytology)
Pleomorphism is a term used in histology and cytopathology to describe variability in the size and shape of cells and/or their nuclei. It is a feature characteristic of malignant neoplasms....
. The nuclei
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
are characteristically extremely hyperchromatic (darkly stained) and large. The nuclear-cytoplasmic ratio
NC ratio
The nuclear-cytoplasmic ratio is a measurement used in cell biology...
may approach 1:1 instead of the normal 1:4 or 1:6. Giant cells that are considerably larger than their neighbors may be formed and possess either one enormous nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
or several nuclei (syncytia). Anaplastic nuclei are variable and bizarre in size and shape. The chromatin
Chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...
is coarse and clumped, and nucleoli may be of astounding size. More important, mitoses are often numerous and distinctly atypical; anarchic multiple spindles may be seen and sometimes appear as tripolar or quadripolar forms. Also, anaplastic cells usually fail to develop recognizable patterns of orientation to one another (i.e. they lose normal polarity). They may grow in sheets, with total loss of communal structures, such as gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
formation or stratified squamous architecture. Anaplasia is the most extreme disturbance in cell growth encountered in the spectrum of cellular proliferations.