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.
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
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
Squamous cell cancer of the lungs, representing 35-40% of
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.
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
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
Most cancers of the Lungs predominantly
form in the cells of the bronchi; a minority of cases develops in the alveoli.
Amos, C.I., et
association scan of tag SNPs identifies a susceptibility locus for lung cancer at 15q25.1."
Nature Genetics 40.5 (2008): 616-622.
United States. Centers for Disease Control and Prevention. "Lung Cancer." Nov. 6, 2014. http://www.cdc.gov/cancer/lung
Cancer Report 2014.
World Health Organization.
2014. pp. Chapter 1.1. ISBN