What is Lung Cancer?

Lung cancer involves the uncontrolled growth of abnormal cells in the lungs, which causes the formation of a mass called a tumor. Through a process known as angiogenesis tumors divert blood vessels from surrounding tissue and form new vasculature to feed their growth. If a tumor does not attack surrounding tissue and spread, it is considered benign (non-cancerous). Tumors that attack normal tissue and eventually spread to other parts of the body are considered malignant (cancerous).

Lung cancer is a very serious form of cancer (classified as a “carcinoma”) that is often lethal, especially if the cancer has already spread to other bodily organs. The term metastasis refers to cancerous cells breaking off from the original (primary) tumor and causing cancer to grow in new areas, forming metastases (secondary tumors). There are two main types of lung cancer: small cell carcinoma and non-small cell carcinoma. It is important to diagnose which type of cancer a patient has, because that will help determine the course of lung cancer treatment.

Small Cell Lung Cancer

Small cell lung cancer (SCLC), also called oat cell lung cancer, constitutes 20-25% of all lung cancer cases. Small cell carcinoma is strongly linked to smoking. Small cell lung cancer is often found in the layer of lung tissue beneath the mucous membrane. This type of carcinoma develops and metastasizes rapidly. By the time it is diagnosed, small cell lung cancer is more likely to have already formed lung metastases than other types of lung cancer.

Non-Small Cell Lung Cancer

Non-small cell lung cancer ../includes several kinds of cancer – each identified by the type of cell affected. This group ../includes squamous cell (or epidermoid) carcinoma, adenocarcinoma, and large cell carcinoma. These forms of cancer tend to grow and spread less quickly than the small cell variety.

Squamous Cell Carcinoma

Squamous cell or epidermoid carcinoma accounts for more than 30% of lung cancers worldwide, making it the most common kind of lung cancer overall. Chiefly "linked to smoking, squamous cell carcinoma typically starts in the large bronchi and tends to stay confined to the chest for longer than other lung cancers. Because it does not progress as rapidly, epidermoid lung cancer usually has better prognoses and survival rates than other forms.

Adenocarcinoma

Adenocarcinoma is on the rise in the United States. Although the causes of adenocarcinoma are still being studied, this form of non-small cell lung cancer now constitutes approximately 35% of all lung cancer in the US. Adenocarcinoma tumors are frequently found along the outer edges of the lungs and under the lining of the bronchi. The progression rate of adenocarcinoma is average, but the five-year patient survival odds are still less than 10%.

Large Cell Lung Cancer

Large cell lung cancer is the term given to carcinomas that do not fit into the other categories. Largely associated with smoking, these large cell carcinomas are often found in the smaller bronchi. This category accounts for about 15% of lung cancer cases. Large cell lung cancer tends to progress quickly, and the outlook for recovery is frequently unfavorable.

Some less common varieties of lung cancer are carcinoid tumor and bronchioalveolar carcinoma. Carcinoid tumors form in the glands near the bronchi. Bronchioalveolar carcinoma develops around scars on the outer edges of the lungs.

Lung cancer is now the most common form of cancer diagnosed in the United States, and it causes more deaths than any other cancer among men and women. Lung cancer makes up 14% of all cancers and 28% of cancer deaths. This is because lung cancer is usually diagnosed when it is already too late.