Types of Cancer
There are over 200 different types of cancers which are generally divided according to the site of its origin. Each cancer type is characterized by formation of a malignant tumor (not to be confused with benign tumor which is not carcinogen) which is made of abnormal cell commonly called cancer cells.
Cancer cell are characterized by uncontrolled, very fast and aggressive growth. While the malignant tumors grow they invade and destroy the adjacent tissues, while cancer cells can also spread throughout the body through circulatory or lymphatic systems and form new malignant tumors in other parts of the body.
The site of origin of malignant tumor usually determines the type of a cancer. For example malignant tumor in breast is known as breast cancer, malignant tumor affecting lung is known as lung cancer, etc. Cancer cell can form a tumor virtually in any part of the body, while the most frequent cancer types worldwide (according to the WHO) are :
1. in men - lung, stomach, colorectal, oesophagus and prostate cancers
2. in women - breast, lung, stomach, colorectal and cervical cancers
Besides classification according to the site of origin of the tumor cancer can be also classified as primary and secondary cancers. When cancer cells metastasize they form new tumors in non-adjacent tissues. The tumors caused by metastasized cancer cells are referred as secondary cancer, while the site of original tumor is called the primary cancer.
When the site of malignant tumor is diagnosed cancer types are classified by the type of the cells that resemble the tumor :
1. carcinoma are malignant tumors which are formed by the epithelial cells which are responsible for about 80% of all cancers
2. sarcoma are malignant tumors which derive from connective tissues and arise in connective tissues such as muscle and bones
3. leukemia are malignancies which derive from cancerous proliferation of the white blood cells and do not result lumps like other types of cancers
4. lymphoma are malignant tumors which occur in lymphoid organs such as lymph gland