Cancer is a disorder in which the cells present in the body multiply abnormally and uncontrollably and tend to invade the other tissues of the body (including the neighbouring tissues, lymph nodes, and distant metastasis) (NCI 2009). The cancer cells do not respond to signals produced by substances involved in growth and multiplication resulting in uncontrollable growth and division of these cells. Usually, the cells in the body tend to die and new cells arise. However, in cancer cells do not die at the right age.
Besides, for the growth and the metabolism of the tumour, new blood vessels are formed that nourish the tumour (Inside Cancer 2009). The cancer can spread from one part of the body to another through the lymph channels, blood, and direct spread (NCI 2009). More than 90 % of all cancer deaths are due to abnormal spread to other parts of the body (Inside Cancer 2009). There are more than 100 types of cancers that can affect different types of tissues or organs present in the body. A cancer cell contains abnormal genetic material brought about by mutation which can result in abnormalities in the rate and growth of the cancer cell.
Usually a cancer is named after that tissue from which it originates. For example, gastric cancer arises from the stomach and basal cell carcinoma arises from the basal cells present in the skin. Cancers can be divided into broader groups namely carcinomas, sarcomas, leukemias, lymphomas, myelomas, etc (NCI 2009). Carcinomas arise from cells of the skin or the mucous membranes. Sarcomas arise from the cells of the supporting tissues of the body such as the blood, bone, cartilage, blood vessels, etc.
Leukemias are cancers that arise from the blood-forming tissues of the body (especially the bone marrow) resulting in abnormalities in the type and number of the blood cells that are produced (Inside Cancer 2009). Lymphoma and myeloma arise from cells that play an important role in the immune system and ensure that body’s defence mechanism (NCI 2009). Leukemias are cancers that arise from the blood-forming tissues of the body including the bone marrow and result in the production of abnormal, immature and very large number of blood cells that enter the bloodstream (NCI 2009).
In the US, about 45000 of new cases of leukemias occur every year and more than 22000 individuals die from the disease (SEER 2009). Leukemias usually arise from the white blood cell types and tend to crowd the peripheral blood. Some of the common symptoms present in leukemias include frequent infections, chronic low-grade fever, weight loss, anorexia, easy bleeding, bruising, malaise, tiredness, etc (Medline 2009). More than 50 % of all leukemias occur over the age of 55 years, and 11 % occur below the age of 20 years. In all age groups, leukemias are more common in males compared to females.
The blood cells present in the bone marrow usually develops from hemopoeitic stem cells. A mutation in the stem cells can result in abnormal growth and uncontrollable division. The cells may not die at the right age. They tend to crowd the peripheral blood. Based on the rapidness and severity of the leukemias, they can be classified into two types namely acute and chronic. Acute leukemias are conditions in which the leukemias cells tend to divide rapidly resulting in fast worsening of the symptoms. Chronic leukemias are conditions in which the leukemic cells divide slowly and the symptoms do not worsen very quickly, having a longer course.
There are four common forms of leukemias. Chronic lymphocytic leukemias (CLL) arise from the lymphoid cells whereas chronic myeloid leukemias (CML) arise from the myeloid cells. These two conditions usually occur in adults. Acute myeloid leukemias (AML) and acute lymphocytic leukemias (ALL) arise from the myeloid cells and the lymphoblast respectively and usually occur in children and young adults. The condition worsens rapidly as the leukemic cells tend to multiple quickly (NCI 2008). Earlier chemotherapy, surgery, radiation and biological therapy was used in the treatment of leukemias to varying degrees of success and prognosis.