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PATHOLOGY PERSPECTIVES HOW COMMON IS IT? Leukemia is diagnosed in about 36,000 Americans every year, and it is responsible for about 22,000 deaths. Although this disease is the leading cause of death from cancer in children, it is much more common in adults. More than 200,000 leukemia patients and survivors are living in the United States today. HOW DOES IT AFFECT THE BODY? Two types of stem cells—myeloid cells and lymphoid cells—manufacture most of our white blood cells in bone marrow. Leukemia occurs when a mutation in the DNA of one or more stem cells in the bone marrow causes the production of multitudes of nonfunctioning leukocytes. Leukemia can be aggressive and quickly progressive, releasing immature cells into the bloodstream (acute), or it can be slowly progressive, leading to the release of mature but nonfunctioning cells (chronic). In either case, the mutated cells do not function as part of the immune system, and they live far longer than normal cells, leading to dangerous accumulations of nonfunctioning cells. Untreated leukemia results in death from excessive bleeding or infection. The uncontrolled bleeding is tied to the suppression of thrombocyte production; the infection risk occurs because, while many white blood cells are present, they are completely nonfunctioning and offer no protection from pathogenic invasion. Many types of leukemia have been identified, but the most common forms are classified into four types: • Acute myelogenous leukemia (AML)— This is an aggressive cancer of the myeloid cells that mainly affects people over 60 years old. The genetic damage that causes AML has been linked to high doses of radiation, chemotherapy for other types of cancer, and exposure to benzene. AML cells can congregate to form a tumor outside the bone marrow. • Chronic myelogenous leukemia (CML)—This is a slowly progressive cancer of the myeloid cells. Unlike other forms of leukemia, CML has been traced to a specific dysfunctional chromosome called the Philadelphia chromosome. Faulty cells can interfere with and slow down normal immune system activity, but they do not usually bring it to a halt. CML occasionally changes its pattern and becomes more aggressive, in which case it is approached as AML. • Acute lymphocytic leukemia (ALL)— This is an aggressive cancer of the lymphocytes. ALL is the type of leukemia found most often among children. The proliferation of cells in a person with ALL is so overwhelming that all other bone marrow activity is suppressed, and immune system function is effectively crippled. Cancerous lymphocytes are released into the blood before they are fully mature. These lymphocytes may gather in lymph nodes, or they may cross into the central nervous system. • Chronic lymphocytic leukemia (CLL)—This is a slowly progressive cancer of the lymphocytes. Although it can involve T cells or natural killer cells, most cases involve B-cell malignancies. CLL is especially common among veterans of the Vietnam War who were exposed to Agent Orange. In some cases, CLL transforms into an aggressive form of lymphoma. LYMPHOMA Lymphoma is a collective name for cancers that start in the lymph nodes. Some types of lymphoma affect the same cells as some types of lymphocytic leukemia, so the delineations between these cancer labels are no longer entirely clear-cut. HOW COMMON IS IT? About 58,000 people will be diagnosed with non-Hodgkin lymphoma this year, and about 20,000 deaths will occur due to this disease. Hodgkin lymphoma is more rare, with about 8,200 diagnoses and 1,300 deaths. HOW DOES IT AFFECT THE BODY? Lymphoma begins with a mutation of the DNA of the affected cells, usually some type of B cell (these account for about 80 percent of cases), T cells, or natural killer cells. The mutated cell begins to replicate, producing massive numbers of nonfunctioning lymphocytes. This causes the lymph tissues to enlarge, and it initiates the other symptoms associated with lymphoma, namely, anemia, night sweats, itchy skin, and fatigue, among others. Mutated cells may travel through the lymphatic system to begin tumors elsewhere: this can occur in other lymph node regions, or in organs like bones, the spleen, or the liver. In some cases, cells can gain access to the central nervous system and begin growing tumors there. A statistical relationship exists between lymphoma and exposure to insecticides, herbicides, fertilizers, and black hair dye, but the direct cause- and-effect sequences have not been established. Lymphoma risk is increased with some infections, including HIV, hepatitis B and C, Epstein-Barr virus, human T-cell lymphotropic virus (HTLV), and helicobactor pylori. Other risk factors for lymphoma include the presence of autoimmune disease, using immune-suppressant drugs, and genetic predisposition. 102 massage & bodywork july/august 2011