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NCHPAD - Building Healthy Inclusive Communities

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Cancer Pathophysiology


Cancer describes a group of more than 150 disease processes characterized by uncontrolled growth and spread of cells. Cancer is not a singular, specific disease but a group of variable tissue responses that result in uncontrolled cell growth (McCance & Roberts, 1998; Fraumeni, 1982). Healthy tissues are composed of cells. Healthy cells have a specific size, structure, function and growth rate that best serves the needs of the tissues they compose. Cancer cells differ from normal cells in size, structure, function, and growth rate. These malignant cells lack the normal controls of growth seen in healthy cells, and grow uncontrollably. This uncontrolled growth allows the cancer cells to invade adjacent structures and then destroy surrounding tissues and organs. Malignant cells may also metastasize to other areas of the body through the cardiovascular or lymphatic systems. This uncontrolled growth and spread of cancer cells can eventually interfere with one or more of a person's vital organs or functions and possibly lead to death. The primary sites of cancer metastasis are the bone, the lymph nodes, the liver, the lungs, and the brain (McCance & Roberts, 1998).

Malignant cells also lose their ability to differentiate or change like normal healthy cells. This inability to differentiate prevents cancer cells from performing the functions required by the tissues and results in a variety of other tissue changes in the body such as pain, cachexia, lowered immunity, anemia, leukopenia, and thrombocytopenia. Some of these changes, such as pain, can be benign but others denote a malignant or premalignant state. Benign neoplasms or tumor cells are made up of the same cell type as the original parent cell, but have abnormal growth rates. Benign cells do not metastasize or invade surrounding tissue. Benign cells can, however, pose a significant problem in the body when they grow too large and compress vital organs or organ systems. The following will describe both malignant and benign tissue changes that occur in the body from abnormal growth and differentiation (McCance & Roberts, 1998).

Dysplasia is a general category that indicates a disorganization of cells. In Dysplasia, a cell varies from its normal parent cell in size, shape, or organization. Dysplasia is often the result of chronic irritation such as the changes seen in cervical tissues from long-standing irritation of the cervix. Metaplasia is the first level of dysplasia (early dysplasia). Metaplasia is a reversible, benign, but abnormal change seen when a cell changes from one type to another. The most common type of metaplasia is in the epithelium of the respiratory tract where columnar epithelial cells change into squamous epithelial cells. Although metaplasia usually gives rise to an orderly arrangement of cells, it may sometimes produce disordered cell patterns. Disorderly cell patterns result in cells of the wrong size, shape or orientation lining up together and may result in inappropriate or faulty tissue behaviors (McCance & Roberts, 1998). Anaplasia is the loss of cellular differentiation. Anaplasia is the most advanced form of metaplasia and is a defining characteristic of malignant cells.

Hyperplasia refers to an increase in the number of cells in a tissue or in a part of a tissue. Hyperplasia, which results in increased tissue size or mass, can be a normal consequence of certain physiologic alterations or it can be a sign of malignancy. Examples of normal hyperplasia are seen in the tissue increases that occur during wound healing, callus formation following a bone fracture, or breast mass increases during pregnancy. An abnormal hyperplasia response is seen in "Neoplastic Hyperplasia," in which there is an increase in cell mass due to tumor formation (McCance & Roberts, 1998). There are also considerable differences in the growth rates of malignant tumors. Some tumors are very slow-growing, even in a malignant state, and are therefore removed easily. Other tumors may grow slowly at first and then undergo change and continue to grow at a rapid pace. Others tumor types may grow very rapidly throughout their entire existence. Factors that affect tumor growth and development include the status of an individual's immune system, the rate the tumor cells are growing, the number of tumor cells actively spreading, and the rate that the normal tissues are being destroyed by the tumor. Several factors affect normal immune function, including stress, malnutrition, advancing age, and chronic diseases. Cancer itself appears to suppress the immune system both early and late in the disease process (McCance & Roberts, 1998).

As described above, uncontrolled cell growth is a characteristic of cancer. Cellular growth rates are regulated by proteins produced by the genetic material in cells. Genetic material can be altered or mutated by environmental factors, errors in genetic replication or repair processes, or by tumor viruses. Altered or mutated genes are called oncogenes, and it is these oncogenes that allow uncontrolled growth in cells (McCance & Roberts, 1998).


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