Anaplasia (from grc, ἀνά ''ana'', "backward" + πλάσις ''plasis'', "formation") is a condition of cells with poor

cellular differentiation Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular ...

, losing the morphological characteristics of mature cells and their orientation with respect to each other and to

endothelial The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

cells. The term also refers to a group of morphological changes in a cell (nuclear

pleomorphism Pleomorphism may refer to: * Pleomorphism (cytology), variability in the size and shape of cells and/or their nuclei * Pleomorphism (microbiology), the ability of some bacteria to alter their shape or size in response to environmental conditions ...

, altered nuclear-cytoplasmic ratio, presence of

nucleoli The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of s ...

, high proliferation index) that point to a possible

malignant transformation Malignant transformation is the process by which cells acquire the properties of cancer. This may occur as a primary process in normal tissue, or secondarily as ''malignant degeneration'' of a previously existing benign tumor. Causes There are ...

. Such loss of structural differentiation is especially seen in most, but not all, malignant

neoplasm A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

s. Sometimes, the term also includes an increased capacity for

multiplication Multiplication (often denoted by the cross symbol , by the mid-line dot operator , by juxtaposition, or, on computers, by an asterisk ) is one of the four elementary mathematical operations of arithmetic, with the other ones being additi ...

. Lack of differentiation is considered a hallmark of aggressive malignancies (for example, it differentiates

leiomyosarcoma Leiomyosarcoma is a malignant (cancerous) smooth muscle tumor. A benign tumor originating from the same tissue is termed leiomyoma. While leiomyosarcomas are not thought to arise from leiomyomas, some leiomyoma variants' classification is evolv ...

s from leiomyomas). 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 In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s in tissues; in these tumors failure of differentiation, rather than dedifferentiation of specialized cells, account for undifferentiated

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

s. Anaplastic cells display marked

(variability). 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 Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom * Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

or several nuclei (

syncytia A syncytium (; plural syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus) ...

). Anaplastic nuclei are variable and bizarre in size and shape. The

chromatin Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...

is coarse and clumped, and

may be of astounding size. More important,

mitoses In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

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 Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...

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

References

{{Authority control Oncology Induced stem cells

See also

References