STROMA: COMPOSITION, STRUCTURE, TYPES AND CANCER - BIOLOGY - 2025

The stroma is a structural or connective tissue. It has been defined as the structural matrix that supports and shapes the different organs. This type of tissue consists of different types of cells and extracellular products, which together provide mechanical and nutritional support to any organ.

The origin of the stroma is embryological and derives from the mesenchymal tissue. This tissue is part of all body organs and tissues. It does not have specific specific functions, but without it no organ would function properly.

Histological section of the cornea. In the image you can see the corneal substance, also called the corneal stroma. Taken and edited from Maiaeg, from Wikimedia Commons

Their tissues are loose and dense irregular type. Of the various types of contective fabrics, this is the most abundant.

Composition and structure

The stroma is a connective tissue that is made up of a significant amount of extracellular matrix. This matrix is ​​made up of a kind of gel, liquid and viscous, also called amorphous fundamental substance, and fibrous connective tissue.

-Connective tissue fibers

Type I collagen fibers

They are very small in size (up to one millionth of 1 mm) and form chains. They are present in different parts of the body, such as bones and tendons. They provide support, resistance and stretch in the tissues they make up.

Elastic fibers

These types of fibers are quite thin (approximately 0.2 to 1 micron). They refract light and have a yellowish color. The cells that compose it are of mesodermal origin. They are present in arteries, lungs and other organs that need to be elastic and resistant to stress and pressure.

Type III collagen fibers

Fibers characteristic of loose connective tissue are common in the epidermis and in the stroma of different types of glands. It forms 50 nanometer fibers, also called reticular fibers. They have the function of supporting expandable organs such as the stomach.

-Stromal cells

There are two types of cells in the stromal connective tissue, fixed cells and wandering or free cells:

Fixed cells

These cells are characterized by being permanent or fixed in the tissue. They participate in the formation and maintenance of the tissue where they live. Examples of fixed cells are fibroblasts, reticular cells, and fat.

Wandering or free cells

They are cells that reach the tissue through the bloodstream, as part of an immune response to an inflammatory event. Examples of wandering or free cells are macrophages, lymphocytes, and polymorphonuclear granulocytes.

Stromal Connective Tissue Types

Loose

Loose stromal connective tissue is a widely distributed tissue in the body of animals. It is found under the epithelial membrane and the glandular epithelium.

It serves as physical support for the blood vessels and nerves that supply epithelia. They are the main site of the body's inflammatory response.

Dense irregular

They are a group of dense embedded extracellular fibers. They have few cells. It is not very flexible but more resistant to traction.

Parenchyma or stroma

Distinguishing between parenchyma and stroma has often become confusing. The stroma is a supporting and supporting connective tissue that has no specific function.

On the other hand, the parenchyma is known as the part that performs a specific function in the organ. For example, in the brain, the parenchyma would turn out to be the nervous tissue (with a specific function of transmitting information through nerve cells), while the stroma, in this case, would be the blood vessels and connective tissue of the brain.

Stroma types

Corneal stroma

Dense connective tissue typical of the cornea. It has collagen sheets as the main constituent and keratocytes (modified fibroblasts). It has collagen fibrils and highly glycolysylated proteins (proteoglycans).

The corneal stroma is characterized by being inflexible, fibrous and resistant. Its origin is embryonic and arises or is derived from a group of cells called the neural crest.

Ovarian stroma

Connective tissue rich in blood vessels. With elongated, ellipsoidal stromal cells and with relatively narrower extremities than in the central portion. It also has reticular and collagen cells.

Other stromata

Other types of stroma include: epithelial stroma of the kidneys (connective tissue, blood vessels and nerves of the kidney), of the spleen (fibrous connective tissue), of the brain (connective tissue, nerve and blood vessels within the brain), of the thymus, bone marrow and iris.

Cancer and tumors

A scientific study carried out by the Bellvitge Biomedical Research Institute and the Catalan Institute of Oncology (Spain), determined that the cells that make up the stroma facilitate the expansion or spread of cancer in the body.

These researchers observed that healthy cells (stromas) that surround the tumor area of ​​some forms of cancer are found in amounts directly proportional to the aggressiveness of the tumor.

That is, the more aggressive the cancer or tumor, the greater the number of stromal cells surrounding the affected area.

Yet another finding reveals that the stroma makes drug treatment difficult and facilitates the spread of cancer via the bloodstream (Metastasis).

Breast stroma

The stroma in breast cancer is associated with immune cells, fibroblasts, myofibroblasts and macrophages. In pathology, the stroma has been shown to be largely a promoter of mammary tumorigenesis.

Gastrointestinal stromal tumor

This disease directly affects the connective tissue. It arises when the interstitial cells of Cajal become cancerous. These cells are common in the gastrointestinal tract, and cancer can occur from the stomach to the anus.

However, occasionally gastrointestinal stromal cancer can appear in organs such as the liver or pancreas and even the prostate.

Histopathological image of a gastrointestinal stromal tumor, at the level of the stomach. Taken and edited from No machine-readable author provided. KGH assumed (based on copyright claims)., via Wikimedia Commons

Stromal tumor of the sex cords

Considered a very rare type of cancer. It is a cancer that affects both the ovaries and the testicles (in a different percentage).

It arises from sustainable cells (Sertoli cells), granulosa cells, and stromal fibroplasts. In women, the malignant form can occur, which can attack at any age, however it seems to be more frequent in the fertile or postmenopausal stages.

Other cancers related to the stroma

• Metanephric stromal tumor.
• Lymphoid stroma carcinoma.

References

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3. Stroma (histology). Recovered from es.wikipedia.org.
4. Basic Tissue Types. Recovered from siumed.edu.
5. Collagen Recovered from es.wikipedia.org.
6. Stroma of Cornea. Recovered from sciencedirect.com.
7. Stromal cells promote the spread of cancer. Recovered from jano.es.
8. LM Arendt, JA Rudnick, PJ Keller & C. Kuperwasser (2010). Stroma in Breast Development and Disease. Seminars in Cell and Developmental Biology.
9. GIST Gastrointestinal stromal tumors. Recovered from seom.org.