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Lung Cancer  

lung cancer

Lung cancer is a common disease that affects the bronchial cells or, more rarely, the cells lining the alveoli of the lungs. The tumor develops from an initially normal group of cells which are transformed into cancerous due to carcinogenic (causes cancer) attacks or aggressions: tobacco, asbestos (see mesothelioma lung cancer), and others. The transformation causes the cells to become not only malignant but also multiply uncontrollably to form cancerous growth, first in the lungs, and then in other parts of the body if there is no effective treatment to stop its progression. Therefore, an effective lung cancer treatment right after the diagnosis is vital.

Lung cancer screening can help detect the disease early, but, most of the times, the detection is done at an advanced stage (Please see our section lung cancer stages for more details). Although the disease can affect individuals at any age, cancer of lungs usually begins to form in the mid-fifties or sixties. Lung cancer at 30 or below is rare. In fact, people tend to experience lung cancer symptoms when the tumor is already advanced in their body.  


Many factors can lead to the occurrence of the tumor, but smoking is responsible for up to 90% of cases. This is a particularly threatening disease; it tends to easily spread in the rest of the body than other types of cancer. Indeed, all the blood passes through the lungs to be oxygenated, and the lungs are in close contact with several blood and lymph vessels. The lungs oxygenate blood thanks to their air-filled sacs anatomical structure (alveoli), and the liver cleanses toxins and wastes from the blood; no wonder whycancer of lungs and liver tends to impact the entire body of the patients.

Lung cancer is the leading cause of cancer death in Canada and USA, both in men than in women, and the second most common canceramong both men and women in the United States. This cancer can however be very effectively prevented by avoiding or quitting smoking. The bizarre scenario is the fact up to 70% of patients do not quit smoking after diagnosis.

Types of lung cancer


Depending on the group of cells affected, cancer of lungs is categorized in 4 types. Thus, it is necessary to distinguish between primary cancers, which arise from the lungs; secondary cancers, which have developed in another part of the body and then spread to the lungs. The classification below concerns primary cancers:

Squamous cell cancer of the lungs, representing 35-40% of all cases;
Adenocarcinoma of the lungs(pulmonary adenocarcinoma), representing 25-35%;
Large-cell lung carcinomaof the lungs, accounting for 10-15%; 

Small cell carcinoma of the lungs, accounting for 20-25%.

These four categories represent the great majority of lung cancers. The first three are grouped into large cell lung carcinoma(LCLC), and the last one is small cell lung cancer(SCLC). SCLC evolves much faster and is more likely to spread to other organs than LCLC.  


Other rarer forms of lung cancer include carcinoid tumors and mucoepidermoid tumors, representing 1-2% of cases.  


The Lungs

Located at the chest, the lungs allows gas exchange of the body. They are separated by the mediastinum region (a division of the thoracic cavity) which contains the heart, trachea, esophagus, and lymph nodes. The lungs are divided into two main structures: right and left.

The right lung has three lobes against two for the left lung. During inhalation (breathing in), the air comes through the trachea and is distributed in the bronchi, bronchioles and alveoli. The oxygen in the inspired air passes through the alveoli into the blood. The blood then distributes oxygen to all cells of the body. During exhalation (breathing out), the blood returns to the lungs carbon dioxide (CO2) which is rejected by every cell in the body. The gas (CO2) passes through the wall of the alveoli and passes into the bronchi. It then is rejected by the trachea, nose and mouth.

Most cancers of the Lungs predominantly form in the cells of the bronchi; a minority of cases develops in the alveoli.