Myoepithelial cells (sometimes referred to as myoepithelium) are cells usually found in glandular epithelium as a thin layer above the

basement membrane The basement membrane, also known as base membrane, is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tis ...

but generally beneath the luminal cells. These may be positive for

alpha smooth muscle ACTA2 (actin alpha 2) is an actin protein with several aliases including alpha-actin, alpha-actin-2, aortic smooth muscle or alpha smooth muscle actin (α-SMA, SMactin, alpha-SM-actin, ASMA). Actins are a family of globular multi-functional pr ...

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ...

and can contract and expel the secretions of

exocrine glands Exocrine glands are glands that secrete substances onto an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of ...

. They are found in the

sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial s ...

mammary gland A mammary gland is an exocrine gland that produces milk in humans and other mammals. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, human ...

lacrimal gland The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each o ...

s, and

salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...

s. Myoepithelial cells in these cases constitute the basal cell layer of an

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 ...

that harbors the epithelial

progenitor In genealogy, a progenitor (rarer: primogenitor; or ''Ahnherr'') is the founder (sometimes one that is legendary) of a family, line of descent, gens, clan, tribe, noble house, or ethnic group.. Ebenda''Ahnherr:''"Stammvater eines Geschlec ...

. In the case of wound healing, myoepithelial cells reactively proliferate. Presence of myoepithelial cells in a hyperplastic tissue proves the benignity of the gland and, when absent, indicates

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 ...

. Only rare cancers like

adenoid cystic carcinoma Adenoid cystic carcinoma is a rare type of cancer that can exist in many different body sites. This tumor most often occurs in the salivary glands, but it can also be found in many anatomic sites, including the breast, lacrimal gland, human lung, ...

s contains

myoepithelial cells Myoepithelial cells (sometimes referred to as myoepithelium) are cells usually found in glandular epithelium as a thin layer above the basement membrane but generally beneath the lumen (anatomy), luminal cells. These may be positive for ACTA2, alph ...

as one of the

malignant 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 ...

components. It can be found in

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...

ectoderm The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

Markers

Myoepithelial cells are true

epithelial cell Epithelium or epithelial tissue is a thin, continuous, protective layer of Cell (biology), cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial (Mesothelium, mesothelial) tissues line ...

s positive for

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...

s, not to be confused with

myofibroblast A myofibroblast is a cell phenotype that was first described as being in a state between a fibroblast and a smooth muscle cell. Structure Myofibroblasts are contractile web-like fusiform cells that are identifiable by their expression of α-s ...

s which are true

mesenchymal cell Mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells or medicinal signaling cells, are multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage c ...

s positive for

vimentin Vimentin is a structural protein that in humans is encoded by the ''VIM'' gene. Its name comes from the Latin ''vimentum'' which refers to an array of flexible rods. Vimentin is a Intermediate filament#Type III, type III intermediate filamen ...

. These cells are generally positive for

actin (αSMA),

cytokeratin Cytokeratins are keratin proteins found in the intracytoplasmic cytoskeleton of epithelial tissue. They are an important component of intermediate filaments, which help cells resist mechanical stress. Expression of these cytokeratins within ep ...

5/6 and other high

molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

cytokeratins, p63 and caldesmon. Myoepithelial cells are stellate in shape and are also known as basket cells. They lie between the basement membrane and glandular epithelium. Each cell consists of a cell body from which 4-8 processes radiate and embrace the secretory unit. Myoepithelial cells have contractile functions. They help in expelling secretions from the lumen of secretory units and facilitate the movement of saliva in salivary ducts.

Other Cancers Involving This Type of Cell

* Myoepithelioma of the head and neck - A (usually) benign tumor of the head/neck consisting of solely myoepithelial cells. * Epithelial-myoepithelial carcinoma (of the salivary glands) - A low-grade malignant tumor composed of both neoplastic epithelial and neoplastic myoepithelial cells (a biphasic tumor). * Epithelial-myoepithelial carcinoma of the lung- A malignant tumor composed of both epithelial and myoepithelial tissues whose pathology resemble salivary cells. * Adenomyoepithelioma of the breast- A (usually) benign tumor of the breast composed of Myoepithelial and Adeno (glandular) cells. * Myoepithelioma of the Breast- A usually benign or exceedingly rare malignant tumor of the breast which mimics IDC but with cells resembling

adenoid In anatomy, the pharyngeal tonsil, also known as the nasopharyngeal tonsil or adenoid, is the superior-most of the tonsils. It is a mass of lymphoid tissue located behind the nasal cavity, in the roof and the posterior wall of the nasopharyn ...

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

s. If malignant, this is also known as a Myoepithelial Carcinoma.

References

External links

* - "Axillary Sweat Gland: Myoepithelium" * - "thick skin" * "Simple Tubular Coiled" * Cell biology Epithelial cells {{anatomy-stub

Markers

Other Cancers Involving This Type of Cell

See also

References

External links