Cancer is caused due to uncontrolled mitotic division of cells known as cancer cells, which invade and destroy the surrounding tissues. Normally, the cells in the human body grow in a well regulated way. But when cancer sets in, a group of these cells start multiplying irregularly and form tumours (the term usually applied to an abnormal growth of tissues). Cancer refers to the group of diseases characterized by the uncontrolled multiplication of abnormal cells in the body. If such multiplication of cells takes place within a vital organ or tissues, normal functions of such organ or tissues is impaired and this may produce fatal results.

Types of tumours:
A tumour may be a benign or a malignant one.

1- Benign tumour – When tumour does not destroy the tissue in which it originates or does not spread to the distant parts of the body, then it is known as the benign tumour. Such type of tumour can be cured easily. It is usually surrounded by a fibrous capsule. Benign tumours usually do not cause death.
2- Malignant tumour – When a tumour destroys the tissue in which it originates or spreads to distant parts of the body, it is known as the malignant tumour. Such tumour is not cured easily and may cause death.

Types of Cancer:
Cancer may be of following types:
(1) Carcinoma (malignant tumour in the epithelial tissue)
(2) Sarcoma (malignant tumour of connective tissue)
(3) Leukemia (in which the bone marrow produces an increased number of leucocytes)
(4) Lymphoma (malignant tumour in the lymph node.)

Further, the sarcoma may be of fibrous tissue (called fibrosarcoma) or of bone (called osteosarcoma). Carcinomas occur in the epithelial tissues, which cover the body and those forming the inner linings of breast, respiratory and gastro-intestinal tracts, the endocrine glands and of urogenital systems.

Sarcomas develop in the connective tissues including fibrous tissues, adipose or fatty tissues, muscles, blood vessels, bone and cartilage. Rarely a cancer develops in both epithelial and connective tissue and is called a carcinosarcoma. Leukemia is caused when the bone marrow and other blood forming organs produce increased number of certain types of leucocytes. Lymphoma is a cancer of lymphoid tissues. It is caused when the immune cells of the body become cancerous and multiply uncontrollably in a lymph node.

Causes of Cancer:
1.    Cigarette smoking or chewing tobacco cause lung cancer. Beedis are twice as dangerous as cigarettes in causing oral cancer.
2.    Skin cancer may be caused in the waist region due to tightly worn saris and dhotis. ‘Kangri’ under the dress causes abdominal cancer in Kashmiri people. These are due to irritation of the skin.
3.    Oral cancer may be caused due to ill-fitting of teeth in the jaws.
4.    Excessive exposure of skin to sunlight may sometime cause cancer.
5.    Certain chemicals like asbestos, nicotine, caffeine etc. may induce cancer in the body.
6.    Some injuries, if remain for a long time in the body may cause cancer.
7.    Radiation is known to be associated with the some bone sarcomas and leukemia.
8.    Some cancers are believed to be of viral origin. Burkitt’s lymphoma, affecting the jaw bones, is caused by a virus named Epstein-Barr virus. Similarly, the genital horpes affecting the female genital system is caused by a virus.

Symptoms of Cancer:
1.    Presence of persistent lump or thickening anywhere in the body.
2.    A sore, if formed, does not heal up
3.    In females there occurs unusual uterine bleeding and discharge.
4.    There is hoarseness of voice and difficulty in swallowing.
5.    There occurs sudden and rapid change in size and appearance of wart or mole.
6.    There is change in bowel habits.
7.    Remarkable loss of body weight.

Cancer can occur to persons of any age group. But the incidence is higher in persons over 50 years age. Certain types of cancers are hereditary. They are eye-retinoblastoma in children.  Certain other cancer like cancer of kidney in children is congenital. Other hereditary cancers are those in the stomach and colon.

Treatment:
More than 85% of cancers to day are curable if treated in early stage. Treatment depends on the type of tumour, the site of the primary tumour and the extent of spread. The general methods of treatment are surgical removal, radiation and chemotherapy. A new cancer may appear at the same place or in another part of the body after being cured once. Therefore, a patient with a past history of cancer should be re-examined at an interval of every six months.