How does lung cancer develop?

Lung cancer typically develops through a series of stages as abnormal cells in the lungs grow and multiply uncontrollably. Here is a general overview of how lung cancer may develop:

1. Cellular changes: It starts with changes in the DNA of cells in the lungs. These alterations can occur due to various factors such as exposure to carcinogens (cancer-causing substances), smoking, genetic mutations, or environmental pollutants.

2. Precancerous stage (dysplasia): If these cellular changes persist, they can lead to dysplasia, which refers to abnormal growth and development of cells in the lung tissue. Dysplasia can be mild, moderate, or severe.

3. In situ carcinoma: Dysplasia can further progress to in situ carcinoma, also known as non-invasive or pre-invasive lung cancer. During this stage, the abnormal cells are confined to the innermost layer of the bronchial lining and have not yet invaded the surrounding lung tissue.

4. Invasive carcinoma: If the abnormal cells break through the inner layer and start to invade the surrounding lung tissue, it is considered invasive carcinoma or full-blown lung cancer. The cancerous cells can grow into the lung parenchyma (the functional tissue of the lungs), blood vessels, or lymphatic vessels.

5. Metastasis: As lung cancer progresses, cancerous cells can spread to other parts of the body through a process known as metastasis. This occurs when cancer cells break away from the primary tumor and travel through the bloodstream or lymphatic system, establishing new tumors in different organs or tissues. Common sites of metastasis for lung cancer include the liver, brain, bones, lymph nodes, and adrenal glands.

6. Types of lung cancer: Lung cancer can be classified into different types based on the appearance and behavior of the cancerous cells under a microscope. The two main types are:

- Non-small cell lung cancer (NSCLC): This is the most common type, representing about 80-85% of all lung cancer cases. NSCLC includes various subtypes such as adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.

- Small cell lung cancer (SCLC): This is a less common type, accounting for about 10-15% of lung cancer cases. SCLC tends to grow and spread rapidly and is often more aggressive than NSCLC.

It's important to note that lung cancer development can vary among individuals, and the specific sequence of events and progression can be influenced by various factors, including genetic makeup, lifestyle choices, and environmental exposures.