1386 words essay on Causes and Types of Cancer

Cancer has become the second-most killer disease today, killing about seven to eight million people every year in the world. It refers to a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected. The disease harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumours (except in the case of leukaemia where cancer prohibits normal blood function by abnormal cell division in the blood stream).

Tumours can grow and interfere with the digestive, nervous or circulatory systems and they can release hormones that alter body function. Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign.

More dangerous or malignant tumours form when two things occur: one, a cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion, and second, that cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis. When a tumour successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized a serious condition that is very difficult to treat.

In other words, cancer is the result of cells that uncontrollably grow and do not die. They differ from normal cells in the body which follow an orderly path of growth, division, and death. Cancer begins to form when the process of programmed cell death called apoptosis breaks down. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide, leading to a mass of abnormal cells that grows out of control.

Cells can experience uncontrolled growth if there are damages or mutations to DNA, and therefore, damage to the genes involved in cell division. Four key types of gene are responsible for the cell division
process: oncogenes tell cells when to divide, tumour suppressor genes tell cells when not to divide, suicide genes control apoptosis and tell the cell to kill itself if something goes wrong, and DNA-repair genes instruct a cell to repair damaged DNA. Cancer occurs when a cell’s gene mutations make the cell unable to correct DNA damage and unable to commit suicide. Similarly, cancer is a result of mutations that inhibit oncogene and tumour suppressor gene function, leading to uncontrollable cell growth.

Classes of substances that are directly responsible for damaging DNA, promoting or aiding cancer are carcinogens. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to these carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. Theses free radicals damage cells and affect their ability to function normally.

Cancer can also be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life. Age is an important risk factor for cancer as the number of possible cancer-causing mutations in our DNA increases with age.

Several viruses have also been linked to cancer such as: human papilloma virus (a cause of cervical cancer), hepatitis B and C (causes of liver cancer), and Epstein-Barr virus (a cause of some childhood cancers). Human immunodeficiency virus (HIV), that suppresses or weakens the immune system, inhibits the body’s ability to fight infections and increases the chance of developing cancer.

The symptoms of cancer are quite varied and depend on where it is located, where it has spread, and how big the tumour is. Some cancers can be felt or seen through the skin. For example, a lump on the breast or testicle can be an indicator of cancer in those locations. Skin cancer or melanoma is often noted by a change in a wart or mole on the skin. Some oral cancers present white patches inside the mouth or white spots on the tongue. Some brain tumours tend to present symptoms early in the disease as they affect important cognitive functions.

Other cancers have symptoms that are less physically apparent. Pancreas cancers are usually too small to cause symptoms until they cause pain by pushing against nearby nerves or interfere with liver function to cause jaundice. Symptoms also can be created as a tumour grows and pushes against organs and blood vessels. For example, colon cancers lead to symptoms such as constipation, diarrhea, and changes in stool size. Bladder or prostate cancers cause changes in bladder function such as more frequent or infrequent urination.

As cancer cells use the body’s energy and interfere with normal hormone function, it is possible to present symptoms such as fever, fatigue, excessive sweating, anemia, and unexplained weight loss. Since these symptoms are common in several other maladies as well, it becomes difficult to detect the disease in the very first diagnosis.

When cancer spreads, or metastasizes, additional symptoms can present themselves in the newly affected area depending on the location where it has spread. If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. Spreading to the lungs may cause coughing and shortness of breath. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and break easily.

Cancer is classified into five broad groups. Carcinomas are characterized by cells that cover internal and external parts of the body such as lung, breast, and colon cancer. Sarcomas are characterized by cells that are located in bone, cartilage, fat, connective tissue, muscle, and other supportive tissues. Lymphomas are cancers that begin in the lymph nodes and immune system tissues. Leukaemia is a cancer that begins in the bone marrow and often accumulates in the bloodstream. Adenomas are cancers that arise in the thyroid, the pituitary gland, the adrenal gland, and other glandular tissues.

Early detection of cancer can greatly improve the odds of successful treatment and survival. Imaging techniques such as X-rays, CT scans, MRI scans, PET scans, and ultrasound scans are used regularly in order to detect where a tumour is located and what organs may be affected by it.

Sometimes endoscopy (a procedure that uses a thin tube with a camera and light at one end, to look for abnormalities inside the body) is also conducted. However, biopsy i.e. extracting cancer cells and looking at them under a microscope is the only absolute way to diagnose cancer. In practice, molecular diagnostics, biopsies, and imaging techniques are all used together to diagnose cancer.

Once a diagnosis is made, the next step is to find out how far the cancer has spread and determine the stage of the cancer. The stage determines which choices will be available for treatment and informs prognoses.

The most common cancer staging method is called the TNM system T (1-4) indicates the size and directs extent of the primary tumour, N (0-3) indicates the degree to which the cancer has spread to nearby lymph nodes, and M (0-1) indicates whether the cancer has metastasized to other organs in the body. A small tumour that has not spread to lymph nodes or distant organs may be staged as (T1, NO, MO), for example. While most Stage 1 tumours are curable, most Stage 4 tumours are inoperable or untreatable.

There is no single treatment for cancer, and patients often receive a combination of therapies and palliative care including surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or gene therapy.

Cancers that are closely linked to certain behaviors are the easiest to prevent. For example, choosing not to smoke tobacco or drink alcohol significantly lower the risk of several types of cancer most notably lung, throat, mouth, and liver cancer. Skin cancer can be prevented by staying in the shade, and protecting ourselves with a hat and shirt when in the sun, and using sunscreen. Diet is also an important part of cancer prevention and oncologists recommend diets that are low in fat and rich in fresh fruits and vegetables and whole grains. Hepatitis B vaccines prevent the hepatitis B virus, which can cause liver cancer.