Cancer Health Article

Definition

Cancer is not just one disease, but a large group of almost 100 diseases. It is a genetic disease, with two main characteristics of uncontrolled growth of the cells in the human body and the ability of those cells to migrate from the original site and spread to distant sites.

Description

One out of every four deaths in the United States is from cancer. It is second only to heart disease as a cause of death in the United States. About 1.2 million Americans are expected to be diagnosed with cancer each year, of which more than 500,000 are diagnosed as terminally ill. Cancer can attack anyone. Since the occurrence of cancer increases as people age, most cases are seen in adults, middle-aged or older. The most common cancers are skin cancer, lung cancer, colon cancer, breast cancer (in women), and prostate cancer (in men). In addition, cancer of the kidneys, ovaries, uterus, pancreas, bladder, rectum, blood (leukemia), and lymph nodes (lymphoma) are also included among the 12 major cancers that affect most Americans.

Cancer, by definition, is a disease of the genes. A gene is a small part of DNA, which is the master molecule of the cell. Genes make proteins, which are the ultimate workhorses of the cells. It is these proteins, along with other substances, that allow our bodies to carry out the many processes that permit people to breathe, think, move, etc. Many genes produce proteins that are involved in controlling the processes of cell growth and division. An alteration, or mutation, to the DNA molecule can disrupt the genes and produce faulty proteins. This causes the cell to become abnormal and lose its restraints on growth. The abnormal cell begins to divide uncontrollably and eventually forms a new growth known as a tumor or neoplasm (medical term for cancer meaning "new growth"). In a healthy individual, the immune system can recognize the neoplastic cells and destroy them before they get a chance to divide. However, some mutant cells may escape immune detection and survive to become tumors or cancers.

Tumors are of two types, benign or malignant. A benign tumor is slow growing, does not spread or invade surrounding tissue, and once removed, it does not usually recur. A malignant tumor, on the other hand, invades surrounding tissue and has the capacity to spread to other parts of the body. If the cancer cells have spread to the surrounding tissues, then, even after the primary malignant tumor is removed, it generally recurs either locally or to a distant site. A majority of cancers are caused by changes in the cell's DNA because of damage due to the cell's environment. Environmental factors that are responsible for causing the initial mutation in the DNA are called carcinogens, and there are many types. Some cancers also have a genetic basis. In other words, an individual could inherit faulty DNA from a patient's parents, which could predispose the patient to getting cancer. There is also the two "hit" theory, where there is a combination of a genetic mutation and a stimulation of cell division and/or replication, due to environmental circumstances. While this scientific evidence points to both factors (environmental and genetic) playing a role, less than 10% of all cancers are purely hereditary. Cancers that are known to have a hereditary link are breast cancer, colon cancer, ovarian cancer, and uterine cancer. In late 2001, scientists took one step closer to identifying genetic markers that indicate cancer susceptibility. Called "low penetrance genes," these markers are believed to combine to increase risk for cancer.

There are several different types of cancers. Carcinomas are cancers that arise in the epithelium (the layer of cells covering the body's surface and lining the internal organs and various glands). Ninety percent of human cancers fall into this category. Melanomas are cancers that originate in the skin, usually in the pigment cells

(melanocytes). Sarcomas are cancers of the supporting tissues of the body, such as bone, muscle, and blood vessels. Cancers of the blood and lymph glands are called leukemias and lymphomas respectively. Gliomas are cancers of the nerve tissue.