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Breast Cancer Profiler Main
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One of the distinguishing characteristics of healthy cells is that each grows and divides to form two identical daughter cells without any of their genetic material becoming lost or damaged. This precise and well-choreographed process is called the cell cycle, and, depending on the type of cell, it happens about every 12 to 24 hours. At one part of the cycle, DNA is made to supply the dividing cells with genetic information. This phase lasts several hours and is called the synthesis or S-phase. The phase during which the cell divides is called the mitotic or M phase, and it may last one to two hours. In order to build fully functioning tissue, cells are organized in a precise way. Within a particular body tissue healthy cells are said to be "homogenous," or identical to each other. But when errors occur in the genetic machinery that orchestrates the cell cycle, the new cells being created (known as "offspring") are not normal. They may resemble their parents, but they will not be identical to them or to each other. And as the offspring continue to divide, the differences in their offspring multiply. So in some cells, the dissimilarities become quite pronounced. Since some abnormal cells differ from each other only slightly and some profoundly, the abnormal cells as a whole are described as "heterogeneous." Furthermore, the genetic information in their center, or nucleus, is in such disarray that the cell doesn't develop the ability to function properly, a process known as differentiation, and there is no order or uniformity to their behavior. It explains what scientists mean when they say, "Cancer is a single disease and it is a hundred diseases." As the mutations in the cells' genetic information increases, the abnormal cells become even more resistant to the body's attempts either to repair the damage or cause the malformed cell to self-destruct. Tumors These abnormal cells differ from healthy ones in another important way: they don't stop dividing and die at a certain point (called programmed cell death or "apoptosis") as normal cells do. The abnormal cells continue to grow out of control in a disorderly fashion. Eventually, this uncontrolled growth of cells is capable of invading nearby tissue. At this point, they are malignant, are already developing their own blood supply, and are successfully evading detection by the body's immune system. Benign tumors, on the other hand, are not malignant or cancerous. The cells of a benign tumor do not spread to other parts of the body, or invade neighboring tissue.  Because of the dissimilarity among the individual cells of a tumor, one particular treatment may fail to destroy all breast cancer cells. A therapy that destroys cells dividing at one rate, for example, may fail to disable those that are dividing more slowly. Or a drug that interferes with one step in the cell cycle may not make an impact on cells that don't take that particular step. It is unclear how cells extend from a tumor and break down the "basement membrane," which is the cellular boundary that separates one type of tissue from another. But just as there are several steps in the formation of a tumor, progression or extension of the tumor also appears to be a multistep process. In one of these steps, for example, cancer cells release chemicals called enzymes that dissolve the protein fibers forming the architecture of the basement membrane; this allows the fast-growing cancer cells to pass through into the healthy tissue. Some breast cancer cells then form tumors in the nearby fatty tissue, and some may extend into the chest well. Cells that manage to make their way through the walls of blood and lymphatic vessels can travel to other parts of the body to form tumors. This process is called metastasis.  This content is reviewed regularly. Last Updated 6/6/2007
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