Features Shared by All Cancers
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The term cancer refers to tumors that are made up of malignant cells, cells capable of potentially unlimited growth, of invading neighboring tissues, and of spreading, or metastasizing, to other areas of the body (although the most common skin cancer, basal cell carcinoma, often does not invade or metastasize unless long neglected).
Malignant cells divide with little control. They become bad citizens, stop respecting the borders of their environment, and launch away from their home and settle in an organ where they normally should not be and where regulatory (control) mechanisms of the body should prevent them from settling. This ability to spread beyond their normal bounds distinguishes malignant tumors from so-called benign tumors, which remain encapsulated in the tissue in which they originated. Benign tumors, however, can be dangerous or disease-causing depending on their size and location. |
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While cancer typically occurs late in life, the unusual behavior malignant cells display-growth and spread—are abilities healthy cells require at the beginning of life. Invasion and metastasis are essential during embryonic development when cells have to move through the embryo from one place to another. When those cells reach their destination, though, the genes that made their migration possible are turned off, and the cells normally don’t move again and some don’t even divide again; they simply do the job they became specialized to do, and then die.
But anything that disturbs the intricate mechanisms of regulation and cross regulation of cell growth, death, and the ability to move may lead to a cancer cell. Those mechanisms do become disturbed, however, through a process known ominously as malignant transformation.
Malignant transformation involves the gradual accumulation of genetic mutations that bit by bit weaken and eventually short-circuit one or more of the many biochemical pathways that normally control cell proliferation (production). The slowness of the process is thought to explain why some cancers can take a decade or more to develop (actually, this is probably also a testament to the cell’s ability to repair genetic damage through the use of DNA repair enzymes. As described later, gene mutations that damage DNA repair systems may facilitate the development of cancer).
So although cancer may be 200 different diseases, deep down all these diseases are basically similar.
This article originally appeared in Frontiers (Autumn 1998) a chronicle of cancer programs at The Ohio State University and was adapted for use on NetWellness with permission, 2004.
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