Cancer is among the leading causes of deaths worldwide. It accounted for 7.4 million deaths (around 13% of all deaths) in 2004 (Felix, 2010). It is defined as the uncontrolled growth of abnormal cells in the body. Normally, your body forms new cells as you need them, replacing old cells that die. Sometimes this process goes wrong. New cells grow even when you don't need them, and old cells don't die when they should. These extra cells can form a mass called a tumor except in the case of leukemia where cancer prohibits normal blood function by abnormal cell division in the blood stream. In some cases cancer is preventable by avoidance of the risk factors, control occupational hazards, vaccination, etc. Unfortunately some cancers, like leukemia, are not preventable. Leukemia is commonly known as a cancer of the blood and affects blood-forming cells in the body. Leukemia is a type of cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of blood cells to be produced and enter the bloodstream. These deranged, immature cells accumulate in the blood and within organs of the body and are not able to carry out the normal functions of blood cells. Each year, nearly 27,000 adults and more than 2,000 children in the United States learn that they have leukemia. From 1999–2006, the rate of people dying from leukemia has varied, depending on their race and ethnicity (Center for Disease Control and Prevention , 2010). It is estimated that each year, approximately 30,800 individuals will be diagnosed with leukemia in the United States and 21,700 individuals will die of the disease. Although the overall incidence of leukemia has been declining in the United States, recent reports suggest that incidence rates may be increasing for certain age and racial groups (Center for Disease Control and Prevention , 2010). There is no known cause of leukemia. Scientists are still trying to figure out why some people get leukemia and some don’t .However it seems to develop from a combination of genetic and environmental factors. These risk factors include very high levels of radiation, working with certain chemicals, down syndrome and certain other genetic diseases, human T-cell leukemia virus-I (HTLV-I) .myelodysplastic syndrome and chemotherapy. Leukemia is common among the Caucasian race and lowest among the Koreans, Japanese and Chinese (Felix, 2010). Men are also more likely to get in than women. In order to understand leukemia better, its pathophysiology has to be understood The blood is made up of fluid called plasma and three types of cells and each type has special functions. White blood cells (WBC ) helps the body fight infections and other diseases. Red blood cells (RBC) carry oxygen from the lungs to the body’s tissues and take carbon dioxide from the tissues back to the lungs. The red blood cells give blood its color and finally Platelets (thrombocytes) that help form blood clots that control bleeding. These blood cells are formed in the bone marrow .While some new or immature cells also known as blasts migrate and grow in other parts of the body, some stay in the bone marrow until they mature. In normal people, blood cells are usually produced in an orderly, controlled way. However in leukemia, like in other cancers, the body produces large numbers of abnormal blood cells. In leukemia the abnormal cells are usually the white blood cells. These cells look different form normal cells and do not function like they are supposed to. The abnormal reproduction in the bone marrow stops normal bone marrow production of red blood cells, platelets, and mature leukocytes therefore causing anemia, thrombocytopenia, and leukopenia. Without treatment, the client dies of infection or hemorrhage. There are different types of leukemia and they are grouped based on how quickly the disease develops and gets worse. Acute leukemia has a sudden onset and short duration. The leukemia cells usually cannot do any of the work of normal white blood cells. The number of leukemia cells increases rapidly and thus the acute nature of the disease. Acute leukemia usually worsens quickly. Chronic leukemia on the other hand has a slow onset and the symptoms persist for a period of years. It gets worse slowly. Early in the disease, the leukemia cells can still do some of the work of normal white blood cells. People may not have any symptoms at first but it is usually diagnosed or discovered during a regular checkup. As the number of the cells in the blood increases, the symptoms get worse as well as leukemia gradually. Leukemia can also be grouped based on the type of white blood cell that it affects .Some affect the lymphoid while others affect the myeloid cells. Leukemia that affects lymphoid cells is called lymphoid, lymphocytic, or lymphoblastic leukemia. Leukemia that affects myeloid cells is called myeloid, myelogenous, or myeloblastic leukemia (cite). These are divided into four sub categories. Chronic lymphocytic leukemia (CLL) affects lymphoid cells and usually grows slowly. It almost never affects children and is very rare among people who are younger than 50 years of age. This is the most common form of leukemia in the North America and in Europe. The disease usually is detected accidentally during a doctor's examination for an unrelated complaint. It results from the gradual accumulation of mature, long-lived lymphocytes. Therefore, this cancer is caused not so much by overgrowth as it is by the extreme longevity and build-up of malignant cells (Brain, Kavet, McCormick, Poole, Silverman, Smith, et al. 2003). Chronic myeloid leukemia (CML) affects myeloid cells and usually grows slowly at first. It mainly affects adults. It is also known as a myeloproliferative disorder because it is a disease in which bone marrow cells proliferate (multiply) outside of the bone marrow tissue. It is easy to diagnose, since it has a genetic peculiarity, or marker. The chromose epsonsinle for this abnormality is called the Philadelphia chromosome (Ph1), after the city in which it was discovered. This chromosome causes uncontrolled reproduction and proliferation of all types of white blood cells and platelets. CML is common among the middle- and retirement-aged people. It occasionally affects people in their 20s, but it is rare in the very young((Brain, et al 2003).
Acute lymphocytic (lymphoblastic) leukemia (ALL) affects lymphoid cells and grows quickly. ALL is the most common type of leukemia in young children. It also affects adults. It is also known as acute lymphoblastic leukemia. It is a malignant disease caused by the abnormal growth and development of early non granular white blood cells, or lymphocytes. This form of leukemia is more predominant in children, around the age of 4. Its is also mostly seen in industrialized nations, and is slightly more common among white children and boys. Lastly, acute myeloid leukemia (AML) affects myeloid cells and grows quickly. It is the most common form of adult leukemia but occurs in both adults and children. It also more common in men than in women. The AML blasts do not mature, and they become too numerous in the blood and bone marrow. As the cells build up, they hamper the body's ability to fight infection and prevent bleeding. ((Brain, et al 2003) Leukemia presents itself in different symptoms depending on the type of leukemia. . The person may not realize that anything out of the ordinary is happening because the symptoms can be very vague. These symptoms manifest themselves based on what is going on with the cells. The symptoms include: Headache usually occurs when large numbers of lymphocytes (white cells) collect in the brain and spinal cord. Weakness or tiredness is linked to anemia because of the shortage of healthy red blood cells to supply the muscles with oxygen. Pain in the bones or joints is also another common symptom .This is caused by abnormal white blood cells collecting under a bone's surface or in a joint. Abdominal or lymph-node swelling is caused by large numbers of abnormal white blood cells that collect in the spleen, causing abdominal swelling, or in the lymph nodes causing them to swell. Swollen lymph nodes can be felt from the outside in the armpits and the neck, but lymph nodes that are located deeper in the body can only be found with an MRI or a CT scan. Abdominal swelling can also be felt externally. Easy bruising or bleeding in the gums of petechia onteh ckinis because of thrombocytopenia , that is shortage platelets in the body. Platelets are responsible for clotting of bleed. Leukemia also causes people to be susceptible to infections because the white blood cells are either too many immature to work normally, or there are not usually enough healthy white blood cells to keep the immune system strong. Fevers and chills are secondary to the infections that are present in the system. Weight loss is another symptom present with leukemia .It is caused by the release of certain chemicals caused by leukemia, the toll on the body of frequent infections, and other factors. Even though a person exhibits all these symptoms, they are most often not due to cancer. An infection or other health problems may also cause these symptoms. It cannot be diagnosed until a doctor is see. The doctor will perform conclusive tests and diagnose the patient based on these tests. There are different tools used to diagnose leukemia. These range from a blood test to a biopsy. To diagnose, the doctor performs a physical exam that checks for swollen lymph nodes, spleen, or liver. Blood tests like a complete blood count is also done. Leukemia causes a very high level of white blood cells. It may also cause low levels of platelets and hemoglobin. Despite all these tests , there is only one sure way to diagnose leukemia. It is through a biopsy. A biopsy is performed by the removal of tissue to look for cancer cells (Bubnoff and Duyster , 2010). The doctor removes bone marrow from a large bone , usually the hip bone and a pathologist checks for cancer cells. The bone marrow is either obtained through a bone marrow aspiration or bone marrow biopsy. In the bone marrow aspiration, after a local anesthetic has been administered, the doctor uses a thick, hollow needle to remove samples of bone marrow. On the other hand , the bone marrow biopsy is done by using a hollow needle to remove a small piece of bone and bone marrow. Other tests that can be done include, cytogenetics where they look at the chromosomes in the cells , spinal tap where cerebrospinal fluid is aspirated and checked for leukemia cells and a chest x-ray to check for swollen lymph nodes or other signs around the chest.
There are various options for the treatment of leukemia. The options are watchful waiting, chemotherapy, targeted therapy, biological therapy, and radiation therapy, and stem cell transplant, organ removal like splenectomy. The choice of treatment depends on the type of leukemia (acute or chronic), age, whether leukemia cells were found in your cerebrospinal fluid. It also may depend on certain features of the leukemia cells. People with acute leukemia need to be treated right away. The goal of treatment is to destroy signs of leukemia in the body and make symptoms go away. This is called a remission. After people go into remission, more therapy may be given to prevent a relapse. This type of therapy is called consolidation therapy or maintenance therapy. Many people with acute leukemia can be cured. If you have chronic leukemia without symptoms, you may not need cancer treatment right away. When treatment for chronic leukemia is needed, it can often control the disease and its symptoms. People may receive maintenance therapy to help keep the cancer in remission, but chronic leukemia can seldom be cured with chemotherapy (Bubnoff and Duyster, 2010).However, stem cell transplants offer some people with chronic leukemia the chance. In conclusion leukemia is considered among the most serious forms of cancer. It is however not a death sentence. If it is caught in the earlier stages then the prognosis is great. Survival rates in leukemia have risen dramatically in the last 40 years with improvements in diagnosis and treatment. There are support groups available for the families and patients of this disease. They can get emotional support during treatment as well as in remission. They also provide information and education and offer a place where feelings can be shared in a comfortable and caring environment.

References
Brain, J., Kavet, R., McCormick, D., Poole, C., Silverman, L., Smith, T., et al. (2003). Childhood leukemia: electric and magnetic fields as possible risk factors. Environmental Health Perspectives, 111(7), 962-970. Retrieved from CINAHL Plus with Full Text database. Bubnoff, N., & Duyster, J. (2010). Chronic myelogenous leukemia: treatment and monitoring. Deutsches Ärzteblatt International, 107(7), doi:10.3238/arztebl.2010.0114
Felix, C. (2010). Infant leukemia 2010: A call to action for the west and the "four Asian Tigers". Pediatric Blood & Cancer, 55(7), 1247-1249.
U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999–2006 Incidence and Mortality Web-based Report. Atlanta (GA): Department of Health and Human Services, Centers for Disease Control and Prevention, and National Cancer Institute; 2010. Retrieved November 255,2010, form http://www.cdc.gov/uscs