Lung mass pathophysiology

Lung Mass Microchapters
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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.

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.

Gross Pathology

The most common cause of lung mass is lung cancer. On gross pathology lung mass presents as:

Cross section of a human lung. The white area in the upper lobe is cancer; the black areas indicate the patient was a smoker. Source: https://commons.wikimedia.org/w/index.php?curid=1241252

Microscopic Pathology

Small cell lung carcinoma (microscopic view of a core needle biopsy)