Abnormal, uncontrolled and purposeless division of cells may lead to the formation/ development of mass of undifferentiated cells i.e. tumor. When tumor is malignant, it is described as cancer and has ability to invade other tissues. Cancer harms the body when cancerous cells divide uncontrollably to form new lumps or masses of tissue called neoplasm (except in the case of leukemia). Tumors can grow and interfere with the normal functioning of various organs. They also release secretions which alter body function(s).
It is one of the main killer diseases nowadays. Physicians and researchers who specialize in the study, diagnosis, treatment and prevention of cancer are called oncologists. Tumors may develop anywhere in the body. However, all tumors are not cancerous. There are two types of tumors: Benign or nonmalignant and Cancerous or malignant.
1. Benign or Nonmalignant Tumor :
It grows slowly, may attain quite a large size, but it remains restricted to the site of its origin (localized) and does not spread to other part of the body. This does not necessarily mean that the benign tumors are not troublesome. Some benign tumors are harmful and fatal e.g. brain tumor (A brain tumor may cause death because the brain is squeezed against the hard skull). Moreover, the benign tumors may sometimes become malignant. e.g. Adenoma and Fibroid.
2. Malignant tumor or cancer :
The growth rate of this tumor is rapid and mortality rate is comparatively more than benign tumor. Rapid growth of tumors causes overcrowding and disruption of normal cells. The cancerous cells compete with the normal cells for nutrients and finally kill them. These cells are spread from one organ to other via blood or lymph and form new tumors called secondary tumors. This migratory process is called metastasis.
Types of Cancer:
There are five main types of cancers according to the type of tissue affected.
i. Carcinoma
ii. Sarcoma
iii. Lymphoma
iv. Leukemia
v. Adenocarcinoma
Cancers are named according to the tissue from which they arise.
i. Carcinoma:
Cancer that arise from epithelial tissue covering or lining the body organs is known as carcinoma. It include breast cancer, lung cancer, cancer of stomach, skin cancer. etc.
ii. Sarcoma:
Cancer that arises from connective tissue is called sarcoma. It include bone tumors (osteosarcoma), muscle tumors (myosarcoma), cancer of cartilage (chondrosarcoma) and cancer of adipose tissue (liposarcoma).
iii. Lymphoma:
Cancer that arises from lymphatic tissue, is called lymphoma. It occurs in the lymphatic nodes, spleen and tissues of immune system.
iv. Leukemia:
It is a type of blood cancer in which there is excessive formation of white blood cells (WBCs) or leucocytes in the bone marrow. People suffering from leukemia have very high leucocyte count. The blood contains millions of abnormal immature WBCs or leucocytes that are incapable of fighting infections. There are various types of leukemia such as monocytic leukemia, lymphoblastic leukemia etc.
v. Adenocarcinoma:
Adenocarcinoma cancer arises in thyroid, pituitary, adrenal and other glandular tissues.
Causes of Cancer:
Although, it is still not very clear as to how the cancer is caused, several factors are now known to be cancer- causing i.e. carcinogenic. These factors are as follows.
i. Chemicals : Several chemicals are known to induce cancer. These include nicotine, caffeine, products of combustion of coal and oil. Several polycyclic hydrocarbons, some sex hormone and steroids, if given or secreted in large amounts, may cause cancer. Breast cancer seems to have hormonal relationship. It is more commonly observed in women who avoid breast feeding.
ii. Radiation : The x-rays, gamma-rays, cosmic rays, ultra-violet rays etc. are carcinogenic. Incidence of skin cancer is higher in the people working in very sunny areas due to UV radiation in the sunlight.
iii. Viruses : Viruses causing cancer have genes called viral oncogenes (v-onc genes). These viruses are also called oncogenic viruses. EBV(Epstein-barr virus), HPV (Human papiloma virus) etc.
iv. Oncogenes : Several genes called cellular oncogenes (c-onc genes) or proto-oncogenes have been identified in normal cells which when activated under certain condition could lead to oncogenic transformation of cells.
v. Addiction : Different types addictions likes smoking, chewing of tobacco lead to cancer of mouth, lips and lungs. Alcohol consumption may result in cancer of oesophagus, stomach, intestine and liver. Drugs also cause cancer e.g. Marijuana, anaerobic steroids etc.
c. Treatment of Cancer:
Cancer treatment consists of combination of a number of therapies which are follows:
i. Chemotherapy
ii. Radiotherapy
iii. Surgery
iv. Immunotherapy
v. Supportive therapy
i. Chemotherapy: Chemotherapy comprises administration of certain anticancer drugs. The anticancer drugs check cell division by inhibiting DNA synthesis or are more toxic to cancerous cell than to normal cells. Chemotherapy may lead to hair loss or anaemia but both get corrected after the treatment is stopped.
ii. Radiotherapy: •It is used in addition to chemotherapy. In radiotherapy, the basic principle is to bombard the cancerous tissue or cells with the rays from radioactive materials. For treatment, the cancer tissue or cells are exposed to radiations from radioactive materials such as cobalt, iridium and iodine. The rays- x-rays, gamma rays and charge particles are used to destroy the cancerous tissue or cells but cause minimum damage to the surrounding normal tissue or cells.
iii. Surgery: In surgery, the entire cancerous tissue or cells are removed surgically. It has limited utility. In certain cases such as breast tumor or uterine tumor, the surgery is most effective, but other treatments are also given to kill any cancerous cell that may have been escaped in surgery.
iv. Immunotherapy: Tumor cell have been shown to avoid detection and destruction by immune system. Therefore, the patients are given substances called biological response modifiers such as α-interferon which activates their immune system and helps in destroying the tumor.
v. Supportive therapy: Supportive therapy is used to treat symptoms of cancer and side effects of cancer treatments. Objective of this therapy is to improve the quality of life of cancer patient. This therapy varies depending upon condition of individual patient.
