Lung Cancer

What Is Lung Cancer?


The lungs are a pair of large, spongy, air-filled respiratory organs located on either side of the chest (thorax). They are specialized for gas exchange between our blood and the air. The lungs are covered by a thin layer of tissue called the pleura. A thin layer of fluid acts as a lubricant allowing the lungs to slip smoothly as they expand and contract with each breath.

The lungs expand and contract up to 20 times a minute to supply oxygen all over the body and expel carbon dioxide that has been generated throughout the body.

Parts of the Lungs
The lungs are divided into different parts which are called lobes.

Functions of Lungs

The main function of the lungs is to facilitate exchange of oxygen and carbon dioxide between the air we breathe and the blood. There are a number of other jobs carried out by the lungs that include:

Lung Cancer

Cancer is the uncontrollable growth of abnormal cells that may lead to the formation of a lump or tumor. Cancer starts when any change in the gene forces the cell to grow and multiply uncontrollably. Thus resulting in the growth of a hard mass called tumour. When the cells in the lungs start behaving in an unaccounted manner and continue to grow without dying then it is termed as primary lung cancer. As tumors become larger and more numerous, they undermine the lung’s ability to provide the bloodstream with oxygen.

These tumors may be either benign or malignant. Benign tumors (non cancerous) are comparatively less destructive and cannot spread from its primary location. Malignant tumour is a group of cancer cells that can invade and destroy nearby tissue. They are more dangerous and spread to other parts of the body either through the bloodstream or the lymphatic system. Metastasis refers to cancer spreading beyond its site of origin to other parts of the body. When cancer spreads it is much harder to treat successfully. 

Types of Lung Cancer

Lung Cancer is divided into non-small cell Lung Cancer and small cell Lung Cancer based on the type of cells that is mutated. Non-small cell Lung Cancer is much more common than small cell Lung Cancer.

Non–small cell Lung Cancer

Also known as adenocarcinoma or Squamous cell carcinoma, they account for 80% of Lung Cancer cases. Adenocarcinoma usually starts in glandular cells on the outer part of the lung. They can also start in flat, thin cells called squamous cells. These cells line the bronchi, which are the large airways that branch off from the windpipe (trachea) into the lungs. There are four different types of non–small cell Lung Cancer and each of them have different treatment options:

Squamous cell carcinoma

This is the most common type Lung Cancer in men. This cancer forms in the lining of the bronchial tubes.


This is the most common type of Lung Cancer in women and in non smokers, adenocarcinoma forms in the mucus-producing glands of the lungs.

Bronchioalveolar carcinoma

This is a rare type of adenocarcinoma that forms near the lungs’ air sacs.

Large-cell undifferentiated carcinoma

A rapidly growing cancer, large-cell undifferentiated carcinomas form near the outer edges or surface of the lungs.

Small cell Lung Cancer

These cancers usually start in cells that line the bronchi in the centre of the lungs. The main types of small cell Lung Cancer are small cell carcinoma and combined small cell carcinoma. Small cell Lung Cancer accounts for 20% of Lung Cancer cases and is mostly caused due to smoking.

Anatomy Of Lung Cancer

Occurrence Rate of Lung Cancer

According to National Center for Biotechnology Information (NCBI) reports, Lung Cancer is the second most common cancer and the most common cause of cancer related deaths all over the world. It accounts for 13% of all new cancer cases and 19% of cancer related deaths worldwide. In India, Lung Cancer constitutes 6.9% of all new cancer cases and 9.3% of all cancer related deaths in both sexes. The highest reported incidences of Lung Cancer are from Mizoram in both males and females. The time trends of Lung Cancer show a significant rise in Delhi, Chennai and Bangalore in both sexes.

What Are The Symptoms Of Lung Cancer?

Unfortunately, there are no prominent symptoms of early Lung Cancers. For about 25% of people with Lung Cancer, symptoms are not diagnosed even after having a chest X-ray or CT during a routine test or as a procedure for other problems. Lung Cancer symptoms that may be detected are listed below.

What Are The General Causes Of Lung Cancer?

Lung Cancer occurs when a lung cell’s gene mutation damages the cell’s DNA. Mutations can occur for a variety of reasons. The exact cause of Lung Cancer is still being investigated. However, certain risk factors have been identified to play a major role in causing cells to become cancerous.

Cigarettes and cigarette smoke contain over 70 cancer-causing chemicals (carcinogens). Some of the carcinogens found in cigarette smoke include:
Other known risk factors are
Cigarette Smoking, Lung Cancer and Cilia

Cigarette smoke damages and can kill hair-like projections called cilia. The cilia normally sweep out toxins, carcinogens, viruses, and bacteria. As the cilia get destroyed by continuous smoke, it fails to perform its functions thus allowing items to accumulate in the lungs that may lead to troubles like lung infections or Lung Cancer.

Smoking cessation

is the most important measure that can prevent the development of Lung Cancer. About 90% of the cases of Lung Cancer are attributed to smoking and inhaling of carcinogenic substances so avoiding these factors definitely lowers the risk of getting cancer. For smokers who quit within 10 years the risk of getting Lung Cancer drops to about the same risk as if they had never smoked.


Avoid second hand smoke

Even continual inhalation of the air contaminated with smoke increases the risk of getting Lung Cancer. Avoiding areas where people smoke, such as bars and restaurants, and seek out smoke-free options comes to aid.


A radon free home

High radon levels can be remedied to make your home safer.



Avoid carcinogens at work

Carcinogenic substances increase the risk of Lung Cancer. It is very important to take precautions to protect from exposure to toxic chemicals at work.


Eat a diet full of fruits and vegetables

Opting for a healthy diet with a variety of fruits and vegetables rather that any supplements is a good way to prevent Lung Cancer.



What Are The Stages Of Lung Cancer?

The stage of Lung Cancer refers to the extent to which the cancer has spread in the body. Once the type of the Lung Cancer is determined, then the stage of the cancer is assigned. Stages for non-small cell Lung Cancers are different from small cell Lung Cancers. The stages listed below are taken from the National Cancer Institute’s Lung Cancer staging information:

1. Small Cell Lung Cancer Stages
Small cell Lung Cancer is a comparatively rare Lung Cancer type accounting to less than 20% of Lung Cancers. It often starts in the bronchi, and spreads to other parts of the body, including the lymph nodes. Small cell Lung Cancer stages are classified in two ways:
2. Non-Small Cell Lung Cancer Stages
Non-small cell Lung Cancer is a more common type of Lung Cancer. Non-small cell Lung Cancer staging uses the TNM system with numbers X, 0, 1, 2, 3, or 4 after each letter:

A number (0-4) or the letter X is added as a suffix to each factor indicating the severity of the disease. The letter X indicates that the information could not be assessed while 4 speaks of the high criticality of the disease. Once the T, N and M scores have been revealed, an overall stage is assigned.

Stages of Non Small Cell Lung Cancer

Occult (hidden) stage: In this stage, cancer cells can be spotted in a sputum cytology exam or other test, though the tumor location could not be pinned.

Stage 0 (carcinoma in situ): Cancer cells are only found in the top layer of cells lining air passages and has not crept deeper into the lungs or spread beyond the air passages.

Stage I: A tumor size may be either less than 3cm or range between 3 – 5 cm, but it has not spread to lymph nodes, making it possible for a surgeon to completely remove it. Stage I is divided into 2 sub-stages based on the size of the tumor:
Stage II: There are several ways that stage II Lung Cancer may be diagnosed. One is that the Lung Cancer has spread to lymph nodes near the lungs.

Stage III: Stage III Lung Cancer is found in both the lung and lymph nodes in the middle of the chest. This stage is further divided into two subsets.

Stage IV: The 4th stage is the last and most advanced stage of Lung Cancer. The cancer can be any size, with any of the following characteristics:

Survival Rates Of Lung Cancer?

With no significant symptoms this hideous disease is difficult to detect in its early stages, and treatments for Lung Cancer in its later stages provide a poor prognosis. Lung Cancer has emerged as the leading killer of men and women stricken with invasive cancer.

Non-small cell Lung Cancer (NSCLC)
Stage5 year Survival Rate


Small cell Lung Cancer (SCLC)
Stage5 year Survival Rate


Can Lung Cancer Be Detected Early?

As already mentioned, detecting Lung Cancer at an early stage is not that easy due to its silent nature. A screening test i.e. a procedure for critical evaluation for determining the presence, or spread of the tumor is sometimes helpful in early detection of Lung Cancer. At best, the screening methods find about 30% of Lung Cancers leaving the bulk i.e. rest 70% undetected. In addition, some test results are not clearly diagnostic which can lead to patient concerns and possibly unnecessary biopsies or surgeries. Screening for Lung Cancer is usually accomplished using three methods.

Physical Exam

A physical exam is conducted to look for signs of wheezing, shortness of breath, cough, pain and other possible signs of Lung Cancer. The physical exam will also include the patient’s history of smoking and a chest X-ray.

Sputum Cytology Exam

A sputum cytology exam involves a microscopic examination of a patient’s mucus (sputum).

Spiral CT Exam

In this procedure, a detailed image of the body’s internal workings is taken. The images are then linked to an X-ray machine to create 3D images of the internal organs. These images may reveal potentially cancerous tumors.

Lung Cancer Diagnosis

If the screening tests suggest the possibility of Lung Cancer, definitive diagnostic tests may be done by a pathologist. The pathologist will examine the patient’s lung cells in sputum, phlegm, or from a biopsy sample to type and stage the Lung Cancer.

Lung Cancer: Biopsy

In biopsy, a tissue sample is taken from the suspected cancer. In general, lung biopsies are obtained by either needle biopsy, a lung bronchoscopy technique, or by surgical removal of tissue. Many other tests may be done to get more information about the cancer’s spread.

What Are The Treatments Available?

Adrenal glands are located deep within the body which makes it difficult to detect the growing tumors. However, if the tumor interferes with the regulation of hormones then some symptoms might be visible. There are multiple tests and examinations to ascertain the cause of these symptoms.

Immunotherapy has recently made its way as a successful treatment option for certain Lung Cancers. While most cancer treatments have known side effects, immunotherapy is generally well-tolerated. In general terms, immunotherapy uses the immune system as a treatment against cancer.

What Are The Possible Side Effects Of Lung Cancer Treatment?

The side effects of Lung Cancer treatment depend on the type of treatment opted and the tenure of the treatment. Some common side effects include:

These side effects are usually non persistent and fades away after treatment is finished. There are ways to lessen these side effects. For example, drugs can be used to help prevent or reduce nausea and vomiting.

In most cases the side effects goes away once treatment is over, but in some rare case it may last a long time. If the side effects persist then it is advised to report immediately so that they can be treated promptly.

Is There Curative Treatment For Lung Cancer?

Lung Cancer generally goes undetected till later stages when it becomes almost incurable. Also, Lung Cancers can’t be removed completely by surgery, there is a fair chance of resurrection. In cases when fortunately the cancer gets detected at an early stage, treatment depends on the patient’s overall health. If the patient is in fairly good health then chemotherapy (chemo) combined with radiation therapy is the preferred line of treatment.