August 29, 2023

Fibrosis is a pathological process characterized by the excessive accumulation of fibrous connective tissue in an organ or tissue. This process is part of the body’s natural healing mechanism, typically initiated in response to injury or damage, including chronic inflammation. However, when fibrosis becomes excessive, it can lead to significant impairment of the affected organ’s structure and function, as the normal tissue is replaced by scar tissue.

Common causes of fibrosis

Fibrosis can result from a variety of causes, including:

  • Chronic inflammatory processes: Diseases that cause long-term inflammation in the body, such as chronic hepatitis (liver inflammation) or inflammatory bowel diseases, can lead to fibrosis in the affected organs.
  • Infections: Certain infections can cause prolonged inflammation and subsequent fibrosis, such as tuberculosis.
  • Autoimmune disorders: Diseases where the body’s immune system attacks its own tissues, like rheumatoid arthritis or systemic lupus erythematosus, can lead to fibrotic tissue buildup.
  • Physical injury or trauma: Wounds, surgical incisions, and other forms of physical trauma can initiate the fibrotic healing process.
  • Exposure to toxins or irritants: Chronic exposure to harmful substances, including certain drugs, chemicals, and environmental pollutants, can induce fibrosis in organs like the lungs and liver.
  • Radiation therapy: A cancer treatment that involves radiation can damage tissues and lead to fibrosis as a side effect.

Microscopic appearance of fibrosis

Under the microscope, fibrosis is identified by the presence of excess collagen and other extracellular matrix components that form the fibrous tissue. This tissue appears more dense and structured than the surrounding normal tissue, with fibroblasts (the cells that produce the fibrous tissue) often visible within the matrix. In stained tissue sections, fibrotic areas may appear as bands or patches of pink (eosinophilic) due to the presence of collagen, contrasting with the surrounding tissue’s appearance.

The extent and pattern of fibrosis can vary depending on the cause and the organ involved. For example, in the liver, fibrosis might present as bridging fibrosis connecting neighboring lobules or portal tracts, while in the lungs, it might manifest as a thickening of the alveolar walls. Fibrosis can disrupt the architecture of the affected tissue, leading to functional impairment, as the rigid fibrous tissue cannot perform the normal functions of the original cells.


About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

Other helpful resources

Atlas of pathology
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