Cancer: Definition, Types, Symptoms, Treatement
Definition: Cancer is a generic term given to 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, this is known as metastasis.
The branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer is oncology.
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;
Cancers can be divided in following broad categories:
Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
Lymphoma and myeloma - cancers that begin in the cells of the immune system.
Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.
Cancers begin in cells, the body's basic unit of life. When functioning normally, body cells grow and divide in a controlled way to replace damaged - old cells. Sometimes this cycle malfunctions. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumour. Not all tumours are cancerous; tumours can be benign or malignant.
Benign tumours aren't cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumours do not spread to other parts of the body.
Malignant tumours are cancerous. Cells in these tumours can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis.
Leukemia is an exception to above, it is cancer of bone marrow and blood.
Nearly all cancers are caused by abnormalities in the genetic material of the transformed cells. These abnormalities may be due to the effects of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents. Other cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in all cells from birth. The inheritability of cancers are usually affected by complex interactions between carcinogens and the host's genome. New aspects of the genetics of cancer pathogenesis, such as DNA methylation, and microRNAs are increasingly recognized as important.
Roughly, cancer symptoms can be divided into three groups:
Local symptoms: unusual lumps or swelling (tumour), hemorrhage (bleeding), pain and/or ulceration. Compression of surrounding tissues may cause symptoms such as jaundice (yellowing the eyes and skin).
Symptoms of metastasis (spreading): enlarged lymph nodes, cough and haemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Although advanced cancer may cause pain, it is often not the first symptom.
Systemic symptoms: weight loss, poor appetite, fatigue and cachexia (wasting), excessive sweating (night sweats), anaemia and specific paraneoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.
Diagnosis: Diagnosis usually requires the histologic examination of a tissue biopsy specimen by a pathologist, although the initial indication of malignancy can be symptoms or radiographic imaging abnormalities. Most cancers can be treated and some cured, depending on the specific type, location, and stage.
Treatment: Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy, radiotherapy, immunotherapy, monoclonal antibody therapy or other methods. As research develops, treatments are becoming more specific for different varieties of cancer. There has been significant progress in the development of targeted therapy drugs that act specifically on detectable molecular abnormalities in certain tumours, and which minimize damage to normal cells.