Myoepithelial cells are cells

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 usually found in glandular epithelium as a thin layer above the basement membrane

Basement membrane

The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...

 but generally beneath the lumenal

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

 cells. These may be positive for alpha smooth muscle

ACTA2

Alpha-actin-2 also known as actin, aortic smooth muscle or alpha smooth muscle actin is a protein that in humans is encoded by the ACTA2 gene located on 10q22-q24....

 actin

Actin

Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...

 and can contract and expel the secretions of exocrine glands. They are found in the sweat gland

Sweat gland

Sweat glands, or sudoriferous glands, are small tubular structures of the skin that produce sweat. There are two kinds of sweat glands:...

, mammary gland

Mammary gland

A mammary gland is an organ in mammals that produces milk to feed young offspring. Mammals get their name from the word "mammary". In ruminants such as cows, goats, and deer, the mammary glands are contained in their udders...

, lacrimal gland

Lacrimal gland

The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...

, and salivary gland

Salivary gland

The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

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

Epithelium

Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

 that harbors the epithelial progenitor

Progenitor cell

A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell...

/stem cells. In the case of wound healing

Wound healing

Wound healing, or cicatrisation, is an intricate process in which the skin repairs itself after injury. In normal skin, the epidermis and dermis exists in a steady-state equilibrium, forming a protective barrier against the external environment...

, myoepithelial cells reactively proliferate

Cell growth

The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...

. Presence of myoepithelial cells in a hyperplastic

Hyperplasia

Hyperplasia means increase in number of cells/proliferation of cells. It may result in the gross enlargement of an organ and the term is sometimes mixed with benign neoplasia/ benign tumor....

 tissue proves the benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

ity of the gland and, when absent, indicates cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. Only rare cancers like adenoid cystic carcinoma

Adenoid cystic carcinoma

Adenoid cystic cancer is a rare type of cancer that can exist in many different body sites. It most often occurs in the areas of the head and neck, in particular the salivary glands; but has also been reported in the breast, lacrimal gland of the eye, lung, brain, bartholin gland, trachea, and...

s contains myoepithelial cells as one of the malignant

Malignant

Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...

 components.

It can be found in endoderm

Endoderm

Endoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and mesoderm , with the endoderm as the intermost layer...

 or ectoderm

Ectoderm

The "ectoderm" is one of the three primary germ cell layers in the very early embryo. The other two layers are the mesoderm and endoderm , with the ectoderm as the most exterior layer...

.

Markers

Myoepithelial cells are true epithelial cells positive for keratin

Keratin

Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

s, not to be confused with myofibroblasts which are true mesenchymal cells positive for vimentin

Vimentin

Vimentin is a type III intermediate filament protein that is expressed in mesenchymal cells. IF proteins are found in all metazoan cells as well as bacteria. IF, along with tubulin-based microtubules and actin-based microfilaments, comprise the cytoskeleton...

. These cells are generally positive for alpha smooth muscle actin (αSMA), cytokeratin

Cytokeratin

Cytokeratins are proteins of keratin-containing intermediate filaments found in the intracytoplasmic cytoskeleton of epithelial tissue. The term "cytokeratin" began to be used in the late 1970s when the protein subunits of keratin intermediate filaments inside cells were first being identified and...

 5/6 and other high molecular weight cytokeratins, p63

TP73L

Tumor protein p63 also known as transformation-related protein 63 is a protein that in humans is encoded by the TP63 gene.TP63 also known as the p63 gene was discovered 20 years after the discovery of the p53 tumor suppressor gene and along with p73 constitutes the p53 gene family based on their...

 and caldesmon

Caldesmon

Caldesmon is a protein that in humans is encoded by the CALD1 gene.Caldesmon is a calmodulin binding protein. Like calponin, caldesmon tonically inhibits the ATPase activity of myosin in smooth muscle....

.

External links

- "Axillary Sweat Gland: Myoepithelium" - "thick skin" "Simple Tubular Coiled"