INTRODUCTION

• Cancers are  a  group  of  diseases  characterized uncontrolled growth and spread of abnormal cells. spread of cancer cells this stage is known as metastasis is not controlled, it can result in death.

• Cancer is caused by  many external factors (tobacco, chemicals, radiation  and  infectious organisms) as well as some internal factors (inherited mutations, hormones, immune conditions and random  mutations).  The  causes  of  cancer  are  diverse, complex and only partially understood.

• Many things are known  to  increase the  risk of cancer, including dietary factors,  certain  infections,  lack  of  physical  activity, obesity  and  environmental  pollutants [1].  

• These  factors may act together to initiate or promote carcinogenesis in the human body and thus cancer is leading cause of death.

• Carcinogens: Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. Theses free radicals damage cells and affect their ability to function normally [3].

Types of Cancer : On the Basis of Tissue Effected

• Carcinomas are characterized by cells that cover internal and external parts of the body such as lung, breast and colon cancer. 

• Sarcomas are characterized by cells that are located in bone, cartilage, fat, connective tissue, muscle, and other supportive tissues.

• Lymphomas are cancers that begin in the lymph nodes and immune system tissues. 

• Leukemia’s are cancers that  begin  in  the bone marrow and often accumulate in the bloodstream. 

• Adenomas are cancers that arise in the thyroid, pituitary gland, the adrenal gland and other glandular tissues [3]. 

Screening

• Unlike diagnostic efforts prompted by symptoms and medical signs, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear.[161] This may involve physical examination, blood or urine tests or medical imaging.[161]

• Cancer screening is not available for many types of cancers. Even when tests are available, they may not be recommended for everyone. Universal screening or mass screening involves screening everyone.[162] Selective screening identifies people who are at higher risk, such as people with a family history.[162] Several factors are considered to determine whether the benefits of screening outweigh the risks and the costs of screening.