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Cancer What is cancer? Cancer is overly prolific, abnormal cell growth. Learn about benign, malignant, locally invasive, metastatic, primary and secondary cancers. Share on Facebook. Notice: Users may be experiencing issues with displaying some pages on stanfordhealthcare. We are working closely with our technical teams to resolve the issue as quickly as possible.
Thank you for your patience. View the changes to our visitor policy » View information for Guest Services ». New to MyHealth? Manage Your Care From Anywhere. Activate Account. Create a New Account. Forgot Username or Password? Types of cancer. Genetic testing. What Is Cancer? What is the difference between benign and malignant cancer?
What are "locally invasive cancer" and "metastatic cancer"? Cancer is malignant because it can be "locally invasive" and "metastatic": Locally invasive cancer —The tumor can invade the tissues surrounding it by sending out "fingers" of cancerous cells into the normal tissue.
Metastatic cancer —The tumor can send cells into other tissues in the body, which may be distant from the original tumor. The genetic changes that contribute to cancer usually affect three specific types of gene; proto-oncogenes, tumor suppressor genes, and DNA repair genes. Weinberg, Blood supply : Angiogenesis is defined as the development of new blood vessels that form from pre-existing vasculature.
Angiogenesis is a vital process in normal cells that occurs during development, growth, and wound healing. Below we outline some of the key differences between cancer cells and normal cells. Nandini, D. J Mol Biomark Diagn S Papetti, M. Cancer cells do not respond to these signals. Normal cells are either repaired or die undergo apoptosis when they are damaged or get old.
Cancer cells are either not repaired or do not undergo apoptosis. For example, one protein called p53 has the job of checking to see if a cell is too damaged to repair, and if so, advise the cell to kill itself. If this protein p53 is abnormal or inactive for example, from a mutation in the p53 gene , then old or damaged cells are allowed to reproduce. The p53 gene is one type of tumor suppressor gene that code for proteins that suppress the growth of cells.
Normal cells secrete substances that make them stick together in a group. Normal cells stay in the area of the body where they belong. For example, lung cells remain in the lungs. Some cancer cells may lack the adhesion molecules that cause stickiness, and are able to detach and travel via the bloodstream and lymphatic system to other regions of the body—they have the ability to metastasize.
Once they arrive in a new region such as lymph nodes , the lungs, the liver, or the bones they begin to grow, often forming tumors far removed from the original tumor. Under a microscope, normal cells and cancer cells may look quite different. In contrast to normal cells, cancer cells often exhibit much more variability in cell size—some are larger than normal and some are smaller than normal.
The nucleus appears both larger and darker than normal cells. The reason for the darkness is that the nucleus of cancer cells contains excess DNA. Up close, cancer cells often have an abnormal number of chromosomes that are arranged in a disorganized fashion.
Normal cells reproduce themselves and then stop when enough cells are present. Cancer cells reproduce rapidly before the cells have had a chance to mature. Normal cells mature. Cancer cells, because they grow rapidly and divide before cells are fully mature, remain immature. Doctors use the term undifferentiated to describe immature cells in contrast to differentiated to describe more mature cells.
The degree of maturation of cells corresponds to the grade of cancer. Cancers are graded on a scale from 1 to 3 with 3 being the most aggressive.
When normal cells become damaged, the immune system via cells called lymphocytes identifies and removes them. Cancer cells are able to evade trick the immune system long enough to grow into a tumor by either by escaping detection or by secreting chemicals that inactivate immune cells that come to the scene. Some of the newer immunotherapy medications address this aspect of cancer cells. Normal cells perform the function they are meant to perform, whereas cancer cells may not be functional.
For example, normal white blood cells help fight off infections. In leukemia , the number of white blood cells may be very high, but since the cancerous white blood cells are not functioning as they should, people can be more at risk for infection even with an elevated white blood cell count. The same can be true of substances produced. For example, normal thyroid cells produce thyroid hormone. Cancerous thyroid cells thyroid cancer may not produce thyroid hormone. In this case, the body may lack enough thyroid hormone hypothyroidism despite an increased amount of thyroid tissue.
Angiogenesis is the process by which cells attract blood vessels to grow and feed the tissue. Normal cells undergo a process called angiogenesis only as part of normal growth and development and when new tissue is needed to repair damaged tissue.
Cancer cells undergo angiogenesis even when growth is not necessary. One type of cancer treatment involves the use of angiogenesis inhibitors—medications that block angiogenesis in the body in an effort to keep tumors from growing. This list contains further differences between healthy cells and cancer cells. For those who wish to skip these technical points, please skip to the next subheading labeled summarizing the differences.
Normal cells are controlled by growth tumor suppressors. There are three main types of tumor suppressor genes that code for proteins that suppress growth. One type tells cells to slow down and stop dividing. One type is responsible for fixing changes in damaged cells.
The third type is in charge of the apoptosis noted above. Mutations that result in any of these tumor suppressor genes being inactivated allow cancer cells to grow unchecked.
Normal cells listen to signals from neighboring cells and stop growing when they encroach on nearby tissues something called contact inhibition. Cancer cells ignore these cells and invade nearby tissues. Benign noncancerous tumors have a fibrous capsule. This results in the fingerlike projections that are often noted on radiologic scans of cancerous tumors.
The word cancer, in fact, comes from the Latin word for crab used to describe the crablike invasion of cancers into nearby tissues. Normal cells get most of their energy in the form of a molecule called ATP through a process called the Krebs cycle, and only a small amount of their energy through a different process called glycolysis. Many types of cancer cells produce their energy through glycolysis despite the presence of oxygen Warburg phenomenon.
Thus, the reasoning behind hyperbaric oxygen therapy is flawed. Sometimes hyperbaric oxygen may induce cancer growth. Normal cells are mortal, that is, they have a lifespan. Researchers are beginning to look at something called telomeres , structures that hold DNA together at the end of the chromosomes, for their role in cancer.
One of the limitations to growth in normal cells is the length of the telomeres. Every time a cell divides, the telomeres get shorter. When the telomeres become too short, a cell can no longer divide and the cell dies.
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