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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 ?
When she was 19, cold punch biopsy specimens were obtained under cystoscopic guidance and the histopathological report indicated chronic cystitis and focal intestinal metaplasia.
Lipogranuloma with osseous metaplasia in the breast that developed after "Bu-Hwang" oriental medicine treatment.
Endometrial osseous metaplasia may be more common than is generally accepted.
Additionally the study found a regression in Barrett's metaplasia, and no adverse effects of treatment, confirming the procedure's long-term safety.
The histologic sections were reexamined to confirm the original pathologic diagnosis and to ensure that all cases selected for the bSCC group of the study met the Wain (5) criteria and that cases selected for the BCCm group represented BCC with squamous metaplasia.
Basal cell adenocarcinoma arising in salivary gland metaplasia of the breast: a novel salivary gland-type tumor developing in the breast.
Histologically, the prevalence of intestinal metaplasia in controls was found to be 17%, with over half of the controls having acute or chronic gastric inflammation (Table 3, Fig.
In addition, Helicobacter pylori organisms may be identified in the metaplastic foci, and rarely pancreatic and osseous metaplasia may be identified.
Lack of vitamin A also causes squamous metaplasia, a condition in which the normal pseudostratified, columnar, ciliated respiratory epithelium, which protects the lungs, ears, gut, and most mucous membranes, metamorphoses into squamous cells as on our skin, which doesn't protect these internal structures and can lead to disease.
Mucous cell metaplasia, the increase in the number of goblet cells and amounts of intraepithelial mucus storage, was induced by allergen in both pulmonary and nasal airways and decreased by treatment with gammaT.
SCC of urothelial tract is thought to arise through a process of metaplasia of urothelium.
Although a cervical inlet patch is not considered a premalignant lesion like Barrett metaplasia, it may be symptomatic and should be looked for during esophagoscopy.