What Types of Lung Cancer Exist? Differences between Small Cell & Non Small-Cell Lung Cancer

(April 15th, 2009)

All types of Lung Cancers (also known as Bronchogenic Carcinomas) are classified in to 2 types: i) Small Cell lung cancer ii) Non Small Cell Lung cancer. These names are based on the appearances of malignant tumors within these cells with the look of a microscope. Small cell and non small cell lung cancers appear and grow in different ways, and have very many distinctions, which will be described in this article. Small Cell lung cancers make up about 20% of all lung cancers and are the most aggressive/rapidly growing types of lung cancer out there. Small cell lung cancers are closely related to smoking because 99% of all small cell lung cancers occur in people who smoke. Small cell lung cancers have the tendency to spread to nearby organs and tissues of the body very quickly, thus when small cell lung cancers are diagnosed, they have usually advanced into higher stages.

i) Small Cell Lung Cancer

Small cell lung cancer occurs when malignant tumors form in the tissues of the lungs. Here's how the process works. The lungs that look like cone shaped breathing organs that are found within the chest inhale oxygen in to the body when breathing in, and exhale carbondioxide when breathing out. Each lung has sections called lobes, and the left lung has 2 lobes. The right lung has 3 lobes and is larger. Both lobes of the left and right lungs are surrounded by a thin membrane known as the Pleura. Blood through the lungs is passed to the rest of the body in the form of oxygen through small tubes known as the Bronchi. These thin tubes known as Bronchi contain tiny air sacs that make up the inside of the lungs; they are known as alveoli.There are 2 types of small cell lung cancer, and both divide, grow and spread in different ways. These 2 types of small cell lung cancers are named in the type of cells they are found in as well as how the cells look when viewed under a microscope.

i) Small Cell Carcinoma: This type of small cell lung cancer contains malignant tumor or carcinoma made up of small round or egg shaped cells with little or no cytoplasm. Cytoplasm is a liquid substance that holds all the components of a cell outside of the nucleus.

ii) Combined small cell Carcinoma - This occurs when small cell lung cancer forms malignant tumors around the lungs combined with other types of cells including squamous cell or adenocarcinoma.

Risk Factors for Developing Small Cell Lung Cancer

Smoking is a very high risk factor for developing small cell lung cancer. A risk factor is something that increases your chance of contracting a disease; a risk factor does not mean you will necessarily get the disease; it just increases your chance of developing the disease. Below is a list of complete risk factors for developing small cell lung cancer.

i) Smoking cigarettes, cigars or pipes in earlier or later stages of life.

ii) Exposure to Asbestos via the environment or on the job (occupational exposure).

iii) Exposure to second hand smoke.

Symptoms of Small Cell Lung Cancer

Here is a list of common symptoms of small cell lung cancer.

a) Unusual fatigue or tiredness
b) Loss of appetite
c) Weight loss
d) Coughing up blood
e) Chest pain
f) Breath shortness
g) Face and neck swelling

ii) Non Small Cell Lung Cancer

Non Small Cell lung cancers account for 80% of all types of lung cancers. NSCLCs occur based upon the types of cells they are found in, and come in 3 different types:

a) Adenocarcinomas: Adenocarcinomas are the most common types of non small cell lung cancers making up more than 50%. Mostly, Adenocarcinomas are found in chain smokers but a small percentage of non-smokers also develop this disease. We therefore cannot attribute this type of malignant tumors entirely on smoking, thus other symptoms of this disease also exist. Adenocarcinomas usually develop in the Peripheral area of the lungs while Bronchioloalveolar carcinoma which is a sub-type of Adenocarcinoma develops in the alveolar walls of the lungs.

b) Squamous cell carcinomas: Squamous cell carcinomas develop in the chest areas of the Bronchi and make up 30% of all non small cell lung cancers. Squamous cell carcinomas are commonly associated with skin cancers and scientists see 250,000 new cases of this disease every year in the United States. Elderly or mid-age people are most likely to develop this disease.

Bronchioloalveolar Cell Carcinoma (BAC)

Bronchioloalveolar Cell Carcinoma is a sub-group of malignant tumors of the lungs and accounts for 2% - 9% of all lung cancer tumors. This term was invented by Liebow in 1960 and defines all cancer tumors that show malignant cells growing along existing alveolar walls, have peripheral locations and no other sign of malignant tumor. Dr. Jyoti Patel adds, "BAC was once thought to be an uncommon form of lung cancer, but it appears to be increasing in incidence and more recent studies suggest that it may actually play a role in about one in five of cases of lung cancer."

BAC occurs more frequently in women than in men, and more often in non-smokers than smokers. It is estimated that 1/3rd of all persons with BAC are non smokers in comparison with only 10% of non smokers having lung cancer. Dr. Patel adds, "We'll be watching the never-smokers in our study to see if this holds up. Tobacco-related genetic changes in participants who smoke or have smoked may make them more resistant to this drug."