Introduction

The lungs are two spongy organs surrounded by a thin moist membrane called the pleura. Each lung is composed of smooth, shiny lobes: the right lung has three lobes and the left has two. About 90% of the lung is filled with air; only 10% is solid tissue.

• Air is carried from the trachea (the windpipe) into the lung through flexible airways called bronchi.
• Like the branches of a tree, bronchi divide successively into over a million smaller airways called bronchioles.
• The bronchioles lead to grape-like clusters of microscopic sacs called alveoli.
• In each adult lung, there are about 300 million of these tiny alveoli, which are composed of a thin membrane through which oxygen and carbon dioxide pass to and from capillaries.
• Capillaries, the smallest of our blood vessels, carry blood throughout the body.

The major features of the lungs include the bronchi, the bronchioles and the alveoli. The alveoli are the microscopic blood vessel-lined sacks in which oxygen and carbon dioxide gas are exchanged.

Lung Cancer

Lung cancer develops when genetic mutations occur in a normal cell within the lung, causing it to become abnormal in shape and behavior and to reproduce ceaselessly. Such abnormal cells form a tumor that, if not surgically removed, invades neighboring blood vessels and lymph nodes and spreads to nearby sites. Eventually, the cancer can metastasize to locations throughout the body.

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The two major categories of lung cancer are small cell lung cancer and non-small cell lung cancer. Most lung cancers are non-small cell cancers, which are the subjects of this report. Less common cancers of the lung are known as carcinoids, cylindromas, and certain sarcomas (cancer in soft tissues).