Lung mass pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief:
Overview
A lung mass is defined as an opacity in the lungs that is more than 3 cms (or 1 ½ inches) in size. Lung opacity less than 3 cms are classified as lung nodules.
Pathophysiology
Environmental Factors
Although genetics play a significant role in the pathogenesis of lung mass, it is thought that exposure to environmental risk factors plays an equally important role in the development of lung cancer. The main causes of lung mass include carcinogens (such as those present in tobacco smoke), ionizing radiation, and viral infections. Chronic exposure results in cumulative alterations of DNA in the tissue lining the bronchi of the lungs (the bronchial epithelium). Irreversible DNA changes following exposure to carcinogens are directly associated with the development of lung cancer.[1]
Infection and Inflammation
- There may be a correlation between general inflammation of lung tissue and the development of lung cancers.[2]
- Neutrophils are released in response to bacterial infection and are considered to be the initial responders during inflammation.
- The hypothesis is that neutrophils may activate reactive oxygen or nitrogen species, which can bind to DNA and lead to genomic alterations. Accordingly, inflammation may be thought of as an initiator or promoter of lung cancer development. Also, tissue repair from inflammation is associated with cellular proliferation. During cellular proliferation there may be errors in chromosomal replication that can cause further DNA mutation.
- Angiogenesis, a significant process during tumor growth, may be promoted by chronic states of inflammation, which often require increased blood flow to sites of inflammation.
Genetics
EGFR mutations are seen in about 20%- 50% of lung adenocarcinoma (especially in Asian population)
- EGFR mutations are responsible for the constitutive activation of the tyrosine kinase.
- The most frequent mutations are present in exons 18e21 of the EGFR gene.
- Other mutation involves translocations involving the anaplastic lymphoma kinase (ALK) tyrosine kinase are most frequently EML4-ALK fusions and are seen in estimated 10% of patients with lung adenocarcinoma.
- Genes involved in the pathogenesis of Non Small Cell Carcinoma (NSCC) include mutation in ROS1 gene.
- In Non Small Cell Carcinoma (NSCC), genetic translocations leads to activation of ROS1 gene.
- ROS1 is a receptor tyrosine kinase of the insulin receptor family.
- Other genes involved in pathogenesis of Non Small Cell Carcinoma (NSCC) include mutation in Her2 (ERBB2), BRAF mutations, MET and RET abnormalities.
Associated Conditions
Gross Pathology
The most common cause of lung mass is lung cancer. On gross pathology lung mass presents as:
Microscopic Pathology
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References
- ↑ Dela Cruz CS, Tanoue LT, Matthay RA (2011). "Lung cancer: epidemiology, etiology, and prevention". Clin. Chest Med. 32 (4): 605–44. doi:10.1016/j.ccm.2011.09.001. PMC 3864624. PMID 22054876.
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