What is the Difference Between Granulation Tissue and Granuloma

The main difference between granulation tissue and granuloma is that granulation tissue is an example of fibrovascular proliferation, a part of the tissue repair mechanism, whereas granuloma is a special type of chronic inflammation. Furthermore, granulation tissue consists of small blood vessels and connective tissue while granuloma consists of a circumscribed collection of macrophages, surrounded by lymphocytes.

Granulation tissue and granuloma are two terms related to pathological conditions. Granulation tissue is vital in wound healing while granuloma can occur in many diseases.

Key Areas Covered

1. What is Granulation Tissue
     – Definition, Composition, Function
2. What is Granuloma
     – Definition, Composition, Function
3. What are the Similarities Between Granulation Tissue and Granuloma
     – Outline of Common Features
4. What is the Difference Between Granulation Tissue and Granuloma
     – Comparison of Key Differences

Key Terms

Chronic Inflammation, Connective Tissue, Granulation Tissue, Granuloma, Macrophages, Small Blood Vessels, Wound Healing

What is Granulation Tissue

Granulation tissue is a collection of small, microscopic blood vessels and a connective tissue. Its main function is to facilitate wound healing. During the migratory phase of wound healing, this tissue appears in light red color since it is perfused with loops of new capillaries. The excess granulation tissue is called “proud flesh”. It is soft to touch and moist. It is bumpy in appearance and pulseful in palpation. Usually, granulation tissue is not painful.

Figure 1: Mechanism of Tissue Repair

Factors responsible for the histological appearance of the granulation tissue are the proliferating fibroblasts, angiogenesis (the formation of new, thin-walled delicate capillaries), and infiltrating inflammatory cells in the loose extracellular matrix. Therefore, the functions associated with different cells in the granulation tissue are the formation of extracellular matrix, vascularization, and triggering immune responses respectively.

Here, the extracellular matrix is mainly composed of the type-III collagen, which is weaker but produces rapidly. Later, the type-I collagen, a long-stranded and stronger form of collagen mainly found in scars, replaces these. Furthermore, macrophages and neutrophils are the main immune cells in the granulation tissue. Their function is to phagocytize old and damaged tissue while protecting the wound from pathogenic infections. In addition, the main function of blood vessels in the granulation tissue is the efficient transport of nutrients and oxygen to the growing tissue while removing metabolic wastes. They also help in supplying new leukocytes to the wound area.

What is Granuloma

A granuloma is a special type of chronic inflammation. In general, the three features of a granuloma are the persistence infection, the presence of foreign bodies, and the autoimmunity. The gross appearance of a granuloma is characterized by ulceration, thickening of the wall of the hollow organs, and changes in the texture of the tissue forming necrosis or fibrosis. Moreover, granuloma causes mild clinical presentations as well. Some diseases associated with granulomas are tuberculosis, leprosy, schistosomiasis, sarcoidosis, aspiration pneumonia, etc.

Figure 3: Non-Necrotizing Granuloma in a Lymph Node in the Neck

In a general sense, granuloma occurs with the attempts of the immune system eliminate foreign substance but, unable to do so. This kind of foreign substances can be infectious organisms as well as endogenous substances like necrotic tissue, hair, and keratin. 

Actually, a granuloma is a collection of macrophages surrounded by lymphocytes. In other words, a granuloma surrounds the foreign substances. Here, motile macrophages move from the blood to the site of inflammation. These cells are long-lived. The functions of macrophages are to remove debris and trigger an immune response by serving as antigen-presenting cells and producing cytokines. The two main types of lymphocytes in a granuloma are B cells and T cells. When considering B cells, they differentiate into plasma B cells that produce antibodies. Also, they act along with macrophages to serve as antigen-presenting cells. Also, T cells produce cytokines to attract macrophages and other cells in the immune system. Some granulomas may contain giant cells that are epithelioid histiocytes, fusions of macrophages.

Similarities Between Granulation Tissue and Granuloma

• Granulation tissue and granuloma are two terms related to various pathologic conditions.
• Both aid in curing the disease and preventing its spread.
• Some granulation tissues like vocal cord granuloma, pyogenic granuloma, and intubation granuloma are mistakenly understood as granulomas.

Difference Between Granulation Tissue and Granuloma

Definition

Granulation tissue refers to the new connective tissue and tiny blood vessels that form on the surfaces of a wound during the healing process while granuloma refers to a mass of granulation tissue, typically produced in response to infection, inflammation, or the presence of a foreign substance. Thus, this is the main difference between granulation tissue and granuloma.

Significance

Moreover, granulation tissue is a type of fibrovascular proliferation while granuloma is a special type of chronic inflammation.

Appearance

Granulation tissue is reddish in color, soft, moist, and bumpy while granuloma is cheese-like and visible under the microscope in the central area of the necrosis. Hence, this is also a major difference between granulation tissue and granuloma. 

Clinical Presentations

The clinical presentation is another difference between granulation tissue and granuloma. Granulation tissue is usually painless while granuloma causes a low-grade fever, loss of appetite, loss of weight, loss of function of the affected organs.

Composition

Furthermore, granulation tissue consists of new small blood vessels, fibroblasts, and mononuclear cells in an edematous extracellular matrix while granuloma consists of macrophages surrounded by lymphocytes.

Function

 One other difference between granulation tissue and granuloma is that granulation tissue grows at the base of the wound, aiding in the healing process while the main function of the granuloma is to surround and digest foreign substances.

Conclusion

Granulation tissue is a collection of small blood vessels and connective tissue, which forms as a result of tissue repair response. It is important in wound healing. On the other hand, the granuloma is a collection of macrophages surrounded by lymphocytes. It occurs in the middle of necrosis and is a type of chronic inflammation. It is responsible for surrounding and destroying foreign substances. Therefore, the main difference between granulation tissue and granuloma is their composition and function.  

References:

1. “Granulation Tissue: Definition, Function & Structure.” Biology Dictionary, Biology Dictionary, 1 July 2017, Available Here
2. Steckelberg, James M. “Granuloma: What Does It Mean?” Mayo Clinic, Mayo Foundation for Medical Education and Research, 26 Sept. 2018, Available Here

Image Courtesy:

1. “417 Tissue Repair” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia  
2. “Granuloma mac” By Sanjay Mukhopadhyay – Syracuse, NY (Public Domain) via Commons Wikimedia