What is Cancer?

Every year an estimated 150,000 – 200,000 new patients are diagnosed with cancer in Pakistan. A staggering figure which translates to roughly 500 people per day. Shaukat Khanum Memorial Cancer Hospital (SKMCH) can only accommodate a fraction of them.

Cancer does not discriminate between age, background or gender. So, when it comes to cancer care, neither do we.

Being diagnosed with cancer can be frightening. But understanding what’s going on inside your body can help you feel more in control. Over the years, ongoing research and more effective treatment has increased the survival rate in cancer patients. The better we get at knowing what we’re up against, the higher our chances to beat cancer.

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How cancer starts

Cells in different parts of the body may look and work differently but most reproduce themselves in the same way. They age and die to be replaced by new cells. Genes are what make sure that our cells are growing and dividing in an orderly and controlled manner. But sometimes, a change occurs in the genes when a cell divides. This is what is known as a mutation. Normally a cell can take six different mutations before it turns cancerous.

How cancer grows

Some mutations mean that the cell no longer understands its instructions and starts to grow out of control. Once this happens, the cells carry on dividing and develop into a lump, called a tumour. Tumours can be either benign or malignant. A cancer is a malignant tumour, which occurs in any organ or part of the body. A doctor will be able to tell the difference by examining a small sample of cells under a microscope. This is called a biopsy.

In some cancers, like leukaemia and lymphoma, there are no tumours. These occur from cancerous blood cells, which don’t form solid tumours. Instead, they build up in the blood and sometimes the bone marrow.

How cancer spreads

In a benign tumour, the cells do not spread to other parts of the body and so aren’t cancerous. They can, however, cause problems if they continue to grow in the primary site. The pattern of growth of cancer cells is different. Often they resemble a twisted and distorted version of normal body tissue. These cells divide uncontrollably and have the ability to destroy surrounding body tissue. If untreated, the cancer cells can even break away from the primary cancer and spread to other organs through the bloodstream or lymphatic system. If cancer cells reach a new area, they may go on dividing to form a new tumour. This is known as a secondary cancer or metastasis.

Types of Cancer

Cancer can occur in any organ or part of the body. We’re all familiar with the most common cancers like skin cancer, prostate cancer, lung cancer, breast cancer and colon cancer. These are categorised according to the place the cancer first started. Medically, cancer is also categorised according to the type of cells it started in. There are four main types cancer which occur in the most common types of cells in our bodies.


The majority of cancers (about 85%) are carcinomas. They start in epithelial tissue, which is the tissue that makes up our skin; cover our inner organs and line cavities in our body. The most common forms of cancer – like breast, lung, prostate and bowel cancer – are all carcinomas. There are four different types of epithelial cells and four sub-categories of carcinoma cancer which correspond to them.

  • Squamous cell carcinoma is a cancer which develops in those flat, surface covering cells that line different parts of the body, such as the skin, throat, and oesophagus.
  • Adenocracinoma forms in adenomatous cells. These are the cells in our glands which produce fluids. They are found in organs like the kidneys, stomach, ovaries, and prostate.
  • Transitional cell carcinoma develops in transitional cells, which compose stretchy tissue in organs that expand. They are found in the lining of organs like the bladder and other parts of the urinary system.
  • Basal cell carcinoma is less common. It occurs in cells which form the deepest layer of the skin.

Leukaemia is a cancer which develops in blood forming tissue, like bone marrow. It causes abnormally formed white blood cells that cannot function properly. Too many of these are produced, so they build up in the blood. Leukaemia is one of the less common cancers.


Similar to leukaemia, lymphoma is also characterised by the formation of abnormal white blood cells. It occurs anywhere in the lymphatic system, which is responsible for filtering body fluid and fighting infection. Lymphoma is also a relatively rare form of cancer.


Sarcoma develops in connective or supportive tissue which make up muscles, bones, cartilage, tendons, etc. This is the tissue which supports the body and its organs. There are normally two main types of sarcoma: bone sarcoma, also known as osteosarcoma; and soft tissue sarcomas.