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Transformation of one form of tissue to another.



(1) A permanent transformation of one variety of tissue into another that differs from it morphologically and functionally but preserves its basic species affiliation.

In animals and man, metaplasia is seen only in epithelial and connective tissues, such as in the transformation of cylindrical mucosal epithelium (respiratory, digestive, uterine) into flat, multilayered, cornifying epithelium similar to epidermis, or in the transformation of fibrous connective tissue into fatty, cartilaginous, or bony tissue. Other examples include the ossification of connective-tissue cicatricial adhesions or of the capsules around caseous tubercular foci.

A distinction is made between direct metaplasia, in which one tissue is transformed into another by means of a change in its structural elements, such as the transformation of fibrocytes into osteocytes, and indirect metaplasia, in which the development of new tissue is accomplished by the proliferation of undifferentiated cells, which only later differentiate. Indirect metaplasia most often occurs with regeneration.

The causes of metaplasia are changes in the surrounding medium and in the state of the body tissues (prolonged inflammatory processes, infectious diseases, avitaminosis A, diseases of the hematopoietic organs, hormonal shifts). Metaplasia disrupts normal tissue function and makes possible a subsequent transformation into a rudimentary tumor (anaplasia). The range of phenomena embraced by the concept of metaplasia is strictly defined by some histologists, who include only changes in differentiation on the cellular level (transformation of iris cells into lens; conversion of cells of pigmented retinal epithelium into neural retina, accompanying regeneration of the eye in adult newts).


Eliseev, V. G. SoediniteVnaia tkan’ Gistofiziologicheskie ocherki. Moscow, 1961.
Metaplaziia tkanei. Moscow, 1970. (Collection of articles.)
Strukov, A. I. Patologicheskaia anatomiia, 2nd ed. Moscow, 1971.
(2) Metaplasia, or more commonly in English, metaplasis, is the period of the developmental prime in individual organisms (sexual maturity) or in the history of a group of organisms (expressed in intensive variability and abundance of individuals).
References in periodicals archive ?
from India, in their detailed histological study of chronic gastritis, did not find any association of atrophic gastritis and intestinal metaplasia with other histological features, including Hp infection.
In the present case, pathological analysis of the resected specimen showed three components: Brunner's gland hyperplasia, gastric foveolar metaplasia, and adenocarcinoma in situ.
Intestinal metaplasia was seen in 2 cases (2.0%) which was mild in both patients.
Molecular pathology of breast apocrine carcinomas: a protein expression signature specific for benign apocrine metaplasia. FEBS Lett 2006;580(12):2935-44.
pylori is an etiological factor of intestinal metaplasia and leads to the formation of gastrointestinal phenotype of intestinal metaplasia, explained Dr.
The purpose of this study is to show the significant association of squamous metaplasia (the precursor for cervical cancer), hyperkeratosis, and parakeratosis, and as the Pap smear finding in patients with uterine prolapse, which is sparsely represented in the literature despite the high incidence of the later.
A nasal polyp with osseous metaplasia is a rare finding.
Duodenal contents reflux through the pylorus into the stomach is a physiological phenomenon that occur in the early morning, postprandial periods, and during endoscopy examination.[sup][1],[2] Long-term duodenogastric reflux (DGR) can cause pathological conditions such as chronic gastritis, foveolar hyperplasia, intestinal metaplasia, gastric dysplasia, gastric polyp, and gastric cancer.[sup][3],[4],[5],[6],[7]
The 2015 World Health Organization lung tumor classification (27) was used to classify basal cell hyperplasia (n=64), squamous metaplasia (n=13), moderate dysplasia (n=14), severe dysplasia (n=9), and atypical adenomatous hyperplasia (n=36).
Further development of disregeneration and prolipherative processes in stomach mucous membrane in a view of foci intestinal metaplasia, according to our data, isn't followed by statistical important changes of pepsinogen-1 and gastrin-17 at initial phases and is shifting.
CG is characterized by goblet cells resembling those in the colonic epithelium and it can be combined with intestinal metaplasia. The etiology and treatment of CG have not been clarified yet.