Cancer is a large, heterogeneous class of diseases in which a group of cells display uncontrolled growth, invasion that intrudes upon and destroys adjacent tissues, and
often metastasizes, wherein the tumor cells spread to other locations in the body via the lymphatic system or through the bloodstream. These three malignant properties of cancer differentiate malignant tumors from benign tumors, which do not grow
uncontrollably, directly in vadelocally, or metastasize to regional lymph nodes or distant body sites like brain, bone, liver, or other organs.
What Is Cancer?
Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems. Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start - for example, cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma.
How cancer starts?
Cancer starts when cells in a part of the body start to grow out of control. There are many kinds of cancer, but they all start because of out-of-control growth of abnormal cells.
Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into) other tissues, something that normal cells cannot do. Growing out of control and invading other tissues are what makes a cell a cancer cell.
Cells become cancer cells because of damage to DNA. DNA is in every cell and directs all its actions. In a normal cell, when DNA gets damaged the cell either repairs the damage or the cell dies. In cancer cells, the damaged DNA is not repaired, but the cell doesn't die like it should. Instead, this cell goes on making new cells that the body does not need. These new cells will all have the same damaged DNA as the first cell does.
People can inherit damaged DNA, but most DNA damage is caused by mistakes that happen while the normal cell is reproducing or by something in our environment. Sometimes the cause of the DNA damage is something obvious, like cigarette smoking. But often no clear cause is found.
In most cases the cancer cells form a tumor. Some cancers, like leukemia, rarely form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues where they grow.
How cancer spreads?
Cancer cells often travel to other parts of the body, where they begin to grow and form new tumors that replace normal tissue. This process is called metastasis. It happens when the cancer cells get into the bloodstream or lymph vessels of our body.
How cancers differ?
No matter where a cancer may spread, it is always named for the place where it started. For example, breast cancer that has spread to the liver is still called breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their particular kind of cancer.
Tumours that are not cancer
Not all tumors are cancerous. Tumors that aren't cancer are called benign. Benign tumors can cause problems - they can grow very large and press on healthy organs and tissues. But they cannot invade other tissues hence they can’t spread to other parts of the body (metastasize). These tumors are almost never life threatening.
What Causes Cancer?
Half of all men and one-third of all women in the US will develop cancer during their lifetimes.
Today, millions of people are living with cancer or have had cancer. The risk of developing most types of cancer can be reduced by changes in a person's lifestyle, for example, by quitting smoking, limiting time in the sun, being physically active, and eating a better diet. The sooner a cancer is found and treated, the better the chances are for living for many years.
Types of Cancer
- Bladder cancer
- Brain tumour
- Breast cancer
- Children's cancers
- Gynaecological cancer
- Head and neck cancer
- Kidney (renal) cancer
- Lower gastrointestinal cancers
- Lung cancer
(Hodgkin and non-Hodgkin)
- Prostate cancer
- Skin cancer
- Soft-tissue sarcoma
- Testicular cancer
- Thyroid tumour
- Upper gastrointestinal cancer