However, all tumors are not cancerous. Generally, a tumor first grows as a small swelling and may also become enlarged. According to the nature of growth, tumors may be of two kinds;
• Benign or Non-malignant Tumors: Benign means mild. Benign tumors are not usually fatal. These tumors stay in the region where they began. They do not invade surrounding tissues, although they may push against them as they grow .Their cells do not migrate and form secondary tumors.
• Malignant Tumor: Malignant means fatal. Malignant tumors are cancerous and life threatening. They do not remain confined in any specific tissue. Initially, these tumors grow slowly producing no symptoms of cancer. This stage is called latent stage. The rate of growth of the tumor increases later on. Their cancerous cells begin to compete and destroy normal cells and spread to the neighboring tissues. Finally, the tumors rupture and migrate to other parts of the body with blood and lymph. They invade other tissues and start to grow rapidly to form secondary tumors; the process is called as metastasis.
Types of Cancer:
Cancers can be categorized according to the types of tissue they affect. These are:
• Carcinomas: These are malignant tumors that grow in epithelial tissues like skin and nerves eg. breast cancer, lung cancer, cancer of stomach and pancreas, brain tumors, eye tumor, etc.
• Sarcomas: These are malignant tumors that grow in bone and muscles like bone tumors and muscle tumors.
• Leukemias: These are malignant growth of white blood corpuscles (W.B.Cs.). Persons affected with this cancer show the excessive production of W.B.C. This is also known as blood cancer.
• Lymphomas: It is cancer of lymphoid tissue.
Occurrence: Cancer is very old disease. It has been reported since prehistoric times. Hippocrates described the breast cancer in about seventeenth century A.D. The incidence of cancer increases with age. Cancer is a widely distributed fatal disease of man found in every country of the world. About 2 million people die every year in the world by cancer.
Causative Agents: Any substance that causes cancer is termed as carcinogen. The exact causes of cancer are still unknown, but it is clear that it is neither infectious nor hereditary. The development of cancer seems to depend upon many factors. It may be due to;
• Smoking: Excessive cigarette smoking is one of the major causes of lung cancer. It may also cause the cancer of mouth, throat and larynx.
• Chewing of Tobacco: Most of the mouth cancer has been found due to the chewing of tobacco.
• Physical Irritations or Injuries: Constant irritation or injuries which continue for a long time may produce cancer in that area. For example, the edge of a broken tooth rubbing against the tongue may cause cancer of the tongue at the point of irritation.
• Chemicals: The known carcinogenic chemicals are nicotine, caffeine, coal and oil combustion products and several types of polycyclic hydrocarbons.
• Ultraviolet Rays: Radiations of radio-active elements are reported to produce cancer. Excessive exposure to sunlight may also cause skin cancer.
• Viruses: Some viruses also cause certain human cancers. They have been implicated in various kinds of leukemia.
• Oncogenes: Scientists have recently identified some genes which may cause a normal cell to become cancerous. Such genes are termed as oncogenes. In some cases, oncogenes may be the genes that have a normal function in cell metabolism. If the control of gene expression or an oncogene goes away, the gene may be expressed continually, resulting in the uncontrolled division of a cell. In some way, carcinogens may also interfere with oncogene control and thus cause cancer. Oncogenes result from the mutation of normal genes. Some viruses are called oncogenic viruses as the genes they contain behave like oncogenes.
Some cancers run in families. Scientists believe that hereditary factors and stress may also play in the formation of cancer. If a person inherits a mutant form of such; genes, the cancer is more likely to appear earlier in his life. Hereditary retinoblastoma is a rare cancer which affects children's retinas. It is caused by inheriting one mutant copy of a recessive tumor suppressor gene.
Symptoms: The beginning of cancer (malignant tumor) in the body usually does not show any significant symptom. However, certain disorders of the body have been found to be concerned with cancer which are as follows;
• Any thickening or lump in the breast or elsewhere.
• Abnormal change in a mole or wart.
• Any wound that does not heal for long period of time.
• Unusual bleeding or discharge.
• Persistant indigestion or difficulty in swallowing.
• Persistant cough or hoarseness.
• Any change in normal bowel habits.
Diagnosis: Cancer can be confirmed on the basis of certain pathological examinations. These include biopsy, microscopic examination of body fluids, blood studies and x-ray.
Control: Recent medical researches indicate that cancer can be cured in most of the cases, if diagnosed earlier. Late diagnosis increases the hazards of cancer greatly.
Preventive Methods: The preventive methods are
• To give up smoking & chewing tobacco as these increase the chances of cancer.
• To protect the body from excessive exposure of x-rays, ultra-violet rays, sun¬light, etc.
• To be aware of possible dangerous symptoms mentioned above.
• To have a regular usual medical check-up after the age of forty.
Thus, one may reduce the hazards of cancer by careful self-examinations.
Treatment: The treatment of cancer varies according to the nature of cancer. The common methods used to fight cancer are surgery, radiotherapy and chemotherapy.
• Surgery: Surgery is used to remove most tumors and usually the surrounding tissues, especially for cancer of breasts, colon, lung, stomach & uterus. Some brain tumors can also be removed surgically.
• Radiotherapy: The use of radio-active rays for treatment purposes is called radiotherapy. Some forms of cancer like the cancer of the bladder, cervix, skin and areas of the head and neck can be treated with radiotherapy. The diseased body part is exposed to radiations from x-rays or some other radioactive substances such as cobalt 60. Radiations kill normal cells as well as cancerous ones so care must be taken to administer radiations.
• Chemotherapy: It includes the administration of certain anticancer drugs which either stop the growth of cancer cells or kill them. These are particularly effective against leukemia and lymphomas. Recently, developed effective anticancer drugs are Texal and Taxal taxotere.