New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Cancer

Cancer is a group of diseases in which cells are aggressive (grow and divide without respect to normal limits), invasive (invade and destroy adjacent tissues), and/or metastatic (spread to other locations in the body). These three malignant properties of cancers differentiate them from benign tumors, which are self-limited in their growth and do not invade or metastasize (although some benign tumor types are capable of becoming malignant). Cancer may affect people at all ages, even fetuses, but risk for the more common varieties tends to increase with age. Cancer causes about 13% of all deaths. Apart from people, forms of cancer may affect animals and plants.

Nearly all cancers are caused by abnormalities in the genetic material of the transformed cells. These abnormalities may be due to the effects of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents. Other cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in all cells from birth. Complex interactions between carcinogens and the host genome may explain why only some develop cancer after exposure to a known carcinogen. New aspects of the genetics of cancer pathogenesis, such as DNA methylation, and microRNAs are increasingly being recognized as important.

Genetic abnormalities found in cancer typically affect two general classes of genes. Cancer-promoting oncogenes are often activated in cancer cells, giving those cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments. Tumor suppressor genes are often inactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.

Cancer is usually classified according to the tissue from which the cancerous cells originate, as well as the normal cell type they most resemble. These are location and histology, respectively. A definitive diagnosis usually requires the histologic examination of a tissue biopsy specimen by a pathologist, although the initial indication of malignancy can be symptoms or radiographic imaging abnormalities. Most cancers can be treated and some cured, depending on the specific type, location, and stage. Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy. As research develops, treatments are becoming more specific for different varieties of cancer. There has been significant progress in the development of targeted therapy drugs that act specifically on detectable molecular abnormalities in certain tumors, and which minimize damage to normal cells. The prognosis of cancer patients is most influenced by the type of cancer, as well as the stage, or extent of the disease. In addition, histologic grading and the presence of specific molecular markers can also be useful in establishing prognosis, as well as in determining individual treatments.

Related Stories
 


Health & Medicine News

October 8, 2025

Ancient humans crossing the Bering Strait into the Americas carried more than tools and determination—they also carried a genetic legacy from Denisovans, an extinct human relative. A new study reveals that a mysterious gene called MUC19, inherited ...
Scientists have discovered that bacteria living inside tumors can produce a molecule that fights cancer and enhances chemotherapy. The molecule, called 2-methylisocitrate (2-MiCit), was found to make colorectal cancer cells more vulnerable to ...
Scientists have discovered that DMT, a natural compound found in plants and even the human brain, can dramatically reduce brain damage caused by stroke. The psychoactive molecule, long known for its hallucinogenic effects, restored the blood-brain ...
Researchers in Japan have pinpointed a biological cause of Long COVID brain fog using advanced PET brain imaging. They discovered widespread increases in AMPA receptor density linked to cognitive ...
Addiction often isn’t about chasing pleasure—it’s about escaping pain. Researchers at Scripps Research have discovered that a tiny brain region called the paraventricular nucleus of the ...
Researchers have enhanced vinegar’s antibacterial properties by infusing it with cobalt-based carbon nanoparticles. This nano-boosted solution kills harmful bacteria from both inside and outside their cells while remaining safe for humans. Tests ...
A major study from Tübingen found that prediabetic individuals who normalized their blood sugar through healthy habits — even without shedding pounds — cut their risk of type 2 diabetes by 71%. Researchers discovered that improved fat ...
A chance encounter with plastic waste on a tropical beach sparked a deep investigation into what those fragments mean for human health. The research reveals that bottled water isn’t as pure as it seems—each sip may contain invisible ...
A University of New Mexico scientist is revealing what might be one of the most overlooked causes of dementia — damage in the brain’s tiny blood vessels. Dr. Elaine Bearer has created a new way to classify these changes, showing that many people ...
Scientists studying tiny roundworms have uncovered how the secrets of a long life can be passed from parents to their offspring — without changing DNA. The discovery shows that when certain cellular structures called lysosomes change in ways that ...
Over 40% of fatal crash victims had THC levels far above legal limits, showing cannabis use before driving remains widespread. The rate didn’t drop after legalization, suggesting policy changes haven’t altered risky habits. Experts warn that the ...
A new study shows glioblastoma isn’t confined to the brain—it erodes the skull and hijacks the immune system within skull marrow. The cancer opens channels that let inflammatory cells enter the brain, fueling its deadly progression. Even drugs ...

Latest Headlines

updated 12:56 pm ET