Lung Cancer Basics

The cells of our lungs are constantly growing, dividing and being replaced by newer, healthier cells. This is a highly regulated process that controls the number of cells present in the lungs.

Changes can occur within a cell that cause its growth no longer to be regulated. These abnormally growing cells can form a mass or tumor. Lung cancer occurs when the tumor cells grow into the surrounding, healthy lung tissue.

Types of lung cancer by histologyLung cancers are typically classified as small cell lung cancer (SCLC) or non-small cell lung cancer (NSCLC). Non-small cell lung cancers can be further classified as adenocarcinoma, squamous cell lung cancer, and large cell lung cancer. These classifications are based on the appearance of the tumor cells under a microscope (called histology).

In some lung cancers, a specific genetic mutation can be identified in the cancer cells. Mutations in the KRAS gene occur in approximately 25% of people with NSCLC.