Free online reference notes for students and professional nurses.
Cancer is a general term used to describe a disturbance of cellular growth and refers to a group of diseases and not a single disease entity. There are currently more than 150 different known types of cancer. Because cancer is a cellular disease, it can arise from any body tissue, with manifestations that result from failure to control the proliferation and maturation of cells.
There are four main classifications of cancer according to tissue type: (1) lymphomas (cancers originating in infection-fighting organs), (2) leukemias (cancers originating in blood-forming organs), (3) sarcomas (cancers originating in bones, muscle, or connective tissue), and (4) carcinomas (cancers originating in epithelial cells). Within these broad categories, a cancer is classified by histology, stage, and grade.
Through years of observation and documentation, it has been noted that the metastatic behavior of cancers varies according to the primary site of diagnosis. This behavior pattern is known as the “natural history.” An example is the metastatic pattern for primary breast cancer: breast-bone-lung-liver-brain. Knowledge of the etiology and natural history of a cancer type is important in planning the patient’s care and in evaluating the patient’s progress, prognosis, and physical complaints.
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