What is Cancer?

What is Cancer?

Cancer is a term that is broadly used to describe a collection of more than a hundred related diseases that lead to the uncontrolled growth of abnormal cells in the affected organs.

The human body is made up of a trillion cells, the ‘building blocks of life’ that constitute the basic structural units of any organism. These cells grow and divide to form new ones. When they grow old or get damaged, they die and new cells form in their place.

If this pattern gets disrupted due to genetic changes, cancer develops. The old and damaged cells don’t die, while new ones multiply, hence creating an uncontrolled growth of abnormal cells.

The continuous division of these cells could form masses of tissue, which become a tumour. These can be benign or cancerous. If benign, the tumour can grow but does not spread. Mostly, this can be removed and may not grow back. If cancerous, the tumour can spread to other parts of the body. This is called metastasis, and endangers  life as the cancer could spread to vital organs like the brain, lungs, liver etc. and damage the vital functions necessary to sustain life.

What are the types of cancer?

Cancers are usually named after the organ in which they first form. Broadly, there are four types of cancers:

  • Carcinoma: These are cancers that begin in the skin or the tissues that line the organs
  • Sarcoma: This type of cancer originates in connective tissues like bones, cartilage, blood vessels or muscles.
  • Leukemia: This is a cancer of the bone marrow, which is where blood cells are formed.
  • Lymphoma (these should/can have graphics) or Myeloma: This type of cancer attacks the immune system. 

Cancers are also classified by the organs that they attack. Here are some examples of these types of cancers.

What are the stages of cancer?

Cancers that involve tumours are staged in five broad groups, from 0 to 4. The stages are indicative of how advanced the cancer is. 

  • Stage 0: At this stage, there is no cancerous growth yet. There are abnormal cells present, which have the potential to develop into cancer. 
  • Stage 1: Also referred to as ‘early stage cancer’, at this stage the cancer is restricted to a small part of the affected organ, and has not spread to any other organ. 
  • Stage 2 and 3: By this stage, the cancer has grown to spread into the surrounding tissues or lymph nodes.
  • Stage 4: Also referred to as the advanced stage or metastatic cancer, this stage indicates that the cancer has spread to other parts of the body. 

Cancers that are not related to tumour growth follow their own staging system. Such cancers include blood cancer and lymphomas

Read more about the stages of cancer

What are the causes of cancer?

It is difficult to determine exactly what causes cancer, but there are some factors that increase the risk of cancer

  •       Ageing
  •       Family history of  certain types of cancer
  •       Smoking
  •      Alcoholism 
  •      Consumption of tobacco
  •      Hormones
  •       Obesity
  •       Poor nutrition
  •       Lack of physical activity
  •       Exposure to strong UV radiations
  •       Exposure to chemicals

Some of these factors like ageing and family history are outside our control. Some of the other factors like exposure to radiation, smoking, tobacco consumption, excessive drinking etc can be controlled to prevent cancer.

Read more about the causes of cancer

What are the symptoms of cancer?

The signs and symptoms of cancer vary depending upon which body part or organ that has been affected. Certain common symptoms include:

  •       Sudden and unexpected weight loss
  •       Any persistent change in urine or stool routine
  •       Blood in the stools
  •       Persistent heartburn or indigestion
  •       Lump or thickening in the breast
  •       Changes in skin colour or changes in the shape and size of existing moles
  •       Unusual vaginal bleeding or discharge
  •       Pain or blood during urination
  •      Persistent difficulty in swallowing 
  •      Persistent vomiting
  •      Unexplained bruises or sores that do not heal
  •      Persistent fever or night sweats
  •      Unexplained muscle or joint pains
  •      Hoarseness 
  •      Nagging cough or trouble with breathing

If these symptoms persist, you will need to consult a doctor. Even in the absence of any such symptoms, if you are concerned about your risk of cancer, you can consult a doctor for screening tests that can help detect cancer.

Read more about the symptoms of cancer

What are the different screening tests for cancer?

Screening for cancer refers to undergoing tests for early detection of cancer in apparently healthy population even before the symptoms start to show. Each type of cancer has specific screening tests. Here are some common ones. 

Colonoscopy and Sigmoidoscopy: 

These tests can detect any abnormal growth in the colon even before it becomes cancerous. Thus, it just not helps in early detection of cancer but also in the secondary prevention of cancer. It is recommended that those at risk of colon cancer undergo these tests after the age of 50. 


This test is used to screen for breast cancer. It can identify lumps in the breast even  before these lumps can be felt through self-examination. Although this test cannot prevent cancer, it allows for early detection of cancer, making it easier to treat. 

Low-dose Computed Tomography

This test screens for lung cancer. It is recommended that heavy smokers and former heavy smokers undergo this test once they are over the age of 55. 

Pap Test and Human Papillomavirus Test (HPV)

These tests are conducted alone, or in combination, to screen for cervical cancer. It is recommended that women above the age of 21 undergo this test. It allows for the prevention as well as early detection of abnormal growths, even before they can become cancerous. 

Alpha-fetoprotein Blood Test

This test is recommended for those at high risk of liver cancer. Usually, this is done in combination with an ultrasound of the liver. 

Read more about the screening of cancer

What are the treatment options for cancer?

Treatment depends on the type and stage of the cancer, as well as the overall health of the patient. While some patients may be given just one type of treatment for their cancer, most patients undergo a combination of two or more types of treatments. 

There are three main treatment options for cancer:


This is one of the oldest types of cancer treatments and is still primary treatment used today for most types of cancer. Surgery involves removing the tumor from the body. Surgery may be conducted to take a sample of the tumor, to know the type and stage of cancer. It may also be conducted to remove the entire cancerous growth, or a part of it, from the body. Sometimes, surgery is undertaken to reduce the symptoms of cancer in the patient, thereby improving their quality of life. 

Radiation Therapy

This involves the use of high does of radiation to kill cancer cells or shrink tumors. This therapy often uses high energy x-rays or gamma rays, but protons or other types of energy may also be used. 

Radiation therapy destroys the genetic material that controls the growth of cells. It affects both the healthy and the cancerous cells but the healthy cells are able to recover from the damage.


Chemotherapy uses chemicals to destroy cancer cells. Sometimes a single drug is used for this, but more often a combination of drugs are used in a certain order, to maximize their effect. Chemotherapy is administered through implants, oral medication, injections or through localised treatments, including creams. 

There are advanced treatments for cancer available now. These include immunotherapy, targeted therapy, hormone therapy, stem cell transplant and precision medicine

Read more on cancer treatments