Table of ContentsView AllTable of ContentsTypesMutationsCancer vs. Normal CellsImmune SystemCell ChangesPrecancerous Cells
Table of ContentsView All
View All
Table of Contents
Types
Mutations
Cancer vs. Normal Cells
Immune System
Cell Changes
Precancerous Cells
Cancer cells differ from normal cells in the body in many ways. Normal cells become cancerous when a series of mutations (changes) leads the cells to continue to grow and divide out of control.
This article discusses cancer cells. It explains how cancer cells develop and how they differ from normal cells. It also explains why the body does not recognize and destroy cancer cells as it does other “foreign” cells.
vitanovski / Istockphoto.com
What Is Cancer?Cancer is a disease that occurs when cells become abnormal and grow out of control. Normal cells grow—and then die—when they are given signals to do so. Cancer cells ignore these signals and continue to multiply. Cancer cells also may form a tumor at the original site and then spread and form new tumors in other places.
What Is Cancer?
Cancer is a disease that occurs when cells become abnormal and grow out of control. Normal cells grow—and then die—when they are given signals to do so. Cancer cells ignore these signals and continue to multiply. Cancer cells also may form a tumor at the original site and then spread and form new tumors in other places.
Types of Cancer Cells
There are as many types of cancer cells as there are types ofcancer. Of the hundred-plus types of cancer, most are named for the type of cancer cells in which the disease began.
Carcinomas
Carcinomas are cancers that arise in epithelial cells that line body cavities. The most common type of cancer cells, carcinomas are named after the type of epithelial cells that mutated. These include:
Sarcomas
Sarcomas are cancers that arise in bone, muscle, blood, fat, and other soft tissue cells known as mesenchymal cells. Bone and soft tissue sarcomas include:
Leukemia
Leukemiacells and leukemic blast cells are abnormal white blood cells that form in bone marrow stem cells, where blood cells are made. Unlike some other cancers, leukemia cells do not bind together to form a tumor.
Instead, these abnormal white blood cells build up in the blood and bone marrow, crowding out healthy blood cells. There are four types of leukemia:
Lymphomas
Lymphomasare blood-related cancers that arise from lymphoid tissues in the lymphatic system, a part of the immune system that runs throughout the body.
Lymphomas can develop in different types of white blood cells known as B-cells, T-cells, and NK cells. They can begin anywhere in the body and feed on nutrients in the lymph fluid.
There are two main forms of lymphoma:
Multiple Myeloma
Multiple myeloma is a type of blood cancer that develops in plasma cells—white blood cells that produce antibodies. They occur when a plasma cell becomes abnormal, then divides to replicate, forming myeloma cells.
Myelomas collect in the bone marrow and soft tissue to form a tumor. When it affects several bones, it is known as multiple myeloma. It can also affect other tissues and organs, such as the kidneys.
Causes and Risk Factors of Leukemia
How Do Cancer Cells Form?
2:08Click Play to Learn About the Start and Characteristics of Cancer Cells
2:08
Click Play to Learn About the Start and Characteristics of Cancer Cells
Agenetic predispositionto cancer does not mean you will get cancer. However, if a few mutations are already in place, it will likely take fewer acquired mutations for a cell to become cancerous.
The process of normal cells becoming cancer often goes through stages in which the cell becomes progressively more abnormal in appearance. These stages may include hyperplasia (enlarged) and dysplasia (growing abnormally) before cancer.
Sometimes, this process is described as differentiation. Early on, a cell may look much like normal cells of that organ or tissue. As the progression continues, the cell becomes increasingly undifferentiated. This is why sometimes the original source of cancer cannot be determined.
Recap
How Cancer Cells Divide and Grow
A cancer cell can have thousands of mutations, but only a certain number of these genetic changes in cancer cells cause cancer to divide and grow.Mutations that result in the growth of cancer cells are referred to as “driver mutations,” whereas other mutations are considered “passenger mutations.”
Normal genes that help cells grow, called proto-oncogenes, can become “oncogenes” (or those with the potential to cause cancer) when mutated and drive the growth of cancer. By contrast,tumor suppressor genesare genes within the cell that tell cells to slow down and stop growing and repair damaged DNA. And they tell cells when to die.
RecapMost cancer cells have mutations in both oncogenes and tumor suppressor genes, which lead to their behavior.
Most cancer cells have mutations in both oncogenes and tumor suppressor genes, which lead to their behavior.
Cancer Cells vs. Normal Cells
There are many importantdifferences between cancer cells and normal cells:
May keep growing
May spread to other regions of the body
Can be immortal
Grows when needed
Stays within tissue boundaries
Has a defined lifespan
Growth
Normal cells grow during development stages, such as during childhood, or to repair injured tissue. Cancer cells continue to grow (reproduce) even when further cells are not needed.
Cancer cells also fail to listen to signals that tell them to stop growing or commit “cell suicide” (apoptosis) when the cells become old or damaged. They also ignore signals that tell them to stop dividing and continue to multiply instead.
This is one reason why it can be difficult to surgically remove a cancerous tumor.
Ability to Evade
Cancer cells are able to evade detection from the immune system, which normally hones in on and eliminates abnormal or damaged cells.
In addition to their ability to hide, cancer cells can also trick the immune system into protecting tumors instead of attacking them.
Ability to Spread
Immortality
Most normal cells, like humans, have a limited lifespan. When they reach a certain age, they die. Cancer cells, in contrast, have developed a way to defy death.
At the end of our chromosomes is a structure known as atelomere. Every time a cell divides, its telomeres become shorter. When the telomeres become short enough, the cells die. Cancer cells have figured out a way to restore their telomeres so that they don’t continue to shorten as the cell divides. In this way, they become immortal.
Cancer Cells Hide From the Immune System
Our immune system does not recognize and remove cancer cells as they would a bacteria or virus. This is because cancer cells evolve to avoid detection.
The ability of the immune system to recognize and eliminate cancer cells is thought to be responsible for the uncommon but well-documented phenomena of the disappearance of some cancers without treatment (like thespontaneous remission of cancer.) This process also lies at the crux of the new field of cancer treatment known asimmunotherapy.
Cancer Cells Change
Cancer cells' ability to change is very important in treatment. For example, estrogen-receptor (ER) positive breast cancer may change into ER-negative cancer if it recurs or spreads. This would require a different treatment.
It also helps explain why cancer cells in different parts of a tumor may be different. This is referred to as “heterogenicity” and is important in diagnosis and treatment.
What It Means if You Have Precancerous Cells
An often-confusing condition iscarcinoma-in-situ(CIS). It consists of cells with abnormal changes found in cancer cells. But since they have not spread beyond their original location (or technically, have not gone beyond something called the basement membrane), they are not technically cancer. Since CIS can turn into cancer, it is usually treated as early cancer.
Summary
Cancer cells appear through a series of genetic and environment-induced changes. The process of normal cells becoming cancer often goes through stages in which the cell becomes progressively more abnormal in appearance. But this is just the beginning.
Once cancer has formed, the cells don’t remain the same. Rather, continued mutations may occur. This is why resistance develops to chemotherapy and targeted therapy drugs.
15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
MedlinePlus.Cancer.
Cancer. US National Library of Medicine.
National Cancer Institute.What is cancer?
National Cancer Institute.Cancer stat facts: leukemia.
National Cancer Institute.Cancer stat facts: non-Hodgkin lymphoma.
National Cancer Institute.Cancer stat facts: myeloma.
Medline Plus.What does it mean to have a genetic predisposition to a disease?
Fares J, Fares MY, Khachfe HH, Salhab HA, Fares Y.Molecular principles of metastasis: a hallmark of cancer revisited.Signal Transduct Target Ther. 2020;5(1):28. doi:10.1038/s41392-020-0134-x
American Cancer Society.Changes in genes.
Johns Hopkins Medicine.Overview of cancer.
Adjiri A.Tracing the path of cancer initiation: the AA protein-based model for cancer genesis.BMC Cancer. 2018;18(1):831. doi:10.1186/s12885-018-4739-1.
Gonzalez H, Hagerling C, Werb Z.Roles of the immune system in cancer: from tumor initiation to metastatic progression.Genes Dev. 2018;32(19-20):1267–84. doi:10.1101/gad.314617.118
Peters GJ.Cancer drug resistance: a new perspective. CDR.2018;1:1-5. doi:10.20517/cdr.2018.03.
Meet Our Medical Expert Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?OtherHelpfulReport an ErrorSubmit
What is your feedback?
