Squamous metaplasia is a

benign Malignancy () is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

non-cancerous change (

metaplasia Metaplasia () is the transformation of a cell type to another cell type. The change from one type of cell to another may be part of a normal maturation process, or caused by some sort of abnormal stimulus. In simplistic terms, it is as if the ...

) of surfacing lining cells (

epithelium Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

) to a squamous morphology.

Location

Common sites for squamous metaplasia include the

bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the bladder is a distens ...

and

cervix The cervix (: cervices) or cervix uteri is a dynamic fibromuscular sexual organ of the female reproductive system that connects the vagina with the uterine cavity. The human female cervix has been documented anatomically since at least the time ...

. Smokers often exhibit squamous metaplasia in the linings of their airways. These changes don't signify a specific disease, but rather usually represent the body's response to stress or irritation.

Vitamin A Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most not ...

deficiency or overdose can also lead to squamous metaplasia.

Uterine cervix

In regard to the cervix, squamous metaplasia can sometimes be found in the

endocervix The cervical canal is the spindle-shaped, flattened canal of the cervix which connects the vagina to the main cavity of the uterus in most mammals. Anatomy The cervical canal communicates with the uterine cavity via the internal orifice of the u ...

, as it is composed of

simple columnar epithelium Simple columnar epithelium is a single layer of columnar epithelial cells which are tall and slender with oval-shaped nuclei located in the basal region, attached to the basement membrane. In humans, simple columnar epithelium lines most organs ...

, whereas the ectocervix is composed of stratified squamous non-keratinized epithelium.Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; & Mitchell, Richard N. (2007) ''Robbins Basic Pathology'' (8th ed.). Saunders Elsevier. pp. 716-720

Significance

Squamous metaplasia may be seen in the context of benign lesions (e.g., atypical polypoid adenomyoma), chronic irritation, ''or''

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

(e.g., endometrioid

endometrial carcinoma Endometrial cancer is a cancer that arises from the endometrium (the lining of the uterus or womb). It is the result of the abnormal growth of cells that can invade or spread to other parts of the body. The first sign is most often vaginal ...

), as well as pleomorphic adenoma. File:Cytology of cervical squamous metaplasia.png,

Cytology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living an ...

of squamous metaplasia of the cervix, with typical features. Pap stain. File:Endometrial endometrioid carcinoma with squamous differentiation and keratin granulomas, high magnification.jpg, Endometrial adenocarcinoma (carcinoma at left in image) with squamous differentiation evidenced as necrotic “ghost cells” of keratinocytes at right in image, leaving pink keratin as well as clear spaces at the prior locations of the cell nuclei.

References

{{Pathology Histopathology

Location

Uterine cervix

Significance

See also

References