Cancer cells definition

What is Cancer? Cancer Causes, Types, Treatment, Symptoms & Signs

Cancer is a group of diseases associated with abnormal cell growth that can penetrate or spread to other parts of the body. These contrast with benign tumors that do not spread. Possible signs and symptoms include swelling, abnormal bleeding, prolonged coughing, unexplained weight loss, and a change in bowel movements. Although these symptoms may indicate cancer, they may have other causes. More than 100 types of cancer affect people.

Tobacco use causes about 22% of cancer deaths. Another 10% are associated with obesity, poor nutrition, lack of physical activity, or excessive drinking. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. In developing countries, 15% of cancers are associated with infections such as Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus, Epstein-Barr virus and human immunodeficiency virus (HIV). These factors act, at least in part, by modifying cell genes. Typically, many genetic changes are necessary before the cancer develops. Approximately 5–10% of cancers are associated with inherited genetic defects from a person’s parents. Cancer can be detected by certain signs and symptoms or by screening tests. Then it is usually additionally examined using medical imaging and confirmed by biopsy.

Many types of cancer can be prevented by not smoking, maintaining a healthy weight, not drinking too much alcohol, eating too many vegetables, fruits and whole grains, getting vaccinated against certain infectious diseases, not eating too much processed and red meat, and avoiding too much sun light, Early detection through screening is useful for cervical cancer and colorectal cancer. The benefits of screening for breast cancer are controversial. Cancer is often treated with a combination of radiation therapy, surgery, chemotherapy, and targeted therapy. Pain and symptom management are an important part of treatment. Palliative care is especially important for people with advanced diseases. The probability of survival depends on the type of cancer and the degree of the disease at the beginning of treatment. In children under the age of 15 years, when diagnosed, five-year survival in developed countries averages 80%. For cancer in the United States, the average five-year survival rate is 66%.

In 2015, about 90.5 million people fell ill with cancer. About 14.1 million new cases occur annually (not including skin cancer other than melanoma). This caused about 8.8 million deaths (15.7% of deaths). The most common types of cancer in men are lung cancer, prostate cancer, colorectal cancer, and stomach cancer. In women, the most common types are breast cancer, colorectal cancer, lung cancer, and cervical cancer. If skin cancer, apart from melanoma, was included in the total number of new cases of cancer each year, it would account for about 40% of cases. In children, acute lymphoblastic leukemia and brain tumors are most common, with the exception of Africa, where non-Hodgkin lymphoma is more common. In 2012, about 165,000 children under the age of 15 were diagnosed with cancer. The risk of cancer increases significantly with age, and many types of cancer are more common in developed countries. Rates are rising as more people live to old age and as lifestyle changes in developing countries change. Cancer financial costs were estimated at $ 1.16 trillion per year as of 2010.



Cancer is a large family of diseases that include abnormal cell growth with the possibility of penetration or spread to other parts of the body. They form a subgroup of neoplasms. A neoplasm or tumor is a group of cells that have undergone unregulated growth and often form a mass or lump, but can be distributed diffusely.

All tumor cells show six signs of cancer. These characteristics are necessary for the occurrence of a malignant tumor. They include:

     Cell growth and division in the absence of intrinsic signals
     Continuous growth and separation even with opposite signals
     Avoiding programmed cell death
     Unlimited Cell Divisions
     Promoting the construction of blood vessels
     Tissue invasion and metastasis

Progression from normal cells to cells that can form a detectable mass to direct cancer involves several steps known as malignant progression.

Types Of Cancer offers tailor-made guidelines for more than 120 types of cancer and related hereditary syndromes. Each manual contains comprehensive information approved by oncologists about: introduction, medical illustrations, risk factors, prevention, symptoms and signs, diagnosis, stages, types of treatment, clinical trials, recent studies, solving treatment problems, follow-up care, survival, Questions, which should be assigned to the health team, and additional resources.

The American Society of Clinical Oncology (ASCO) believes that all treatment decisions should be made between patients and their doctors.

Use the menu below to find the guide you are looking for. The first tab offers some common diagnoses, but if you don’t see your specific diagnosis there, please use the Alphabetical Tabs to view the entire list of manuals.

Signs and symptoms


Signs and symptoms of Cancer in Body

When cancer begins, it gives no symptoms. Signs and symptoms appear as weight gain or ulceration. The results obtained depend on the type and location of the cancer. Several symptoms are specific. Many are common in people who have different conditions. Cancer is the “great imitator.” Thus, people diagnosed with cancer often receive treatment for other diseases that were supposed to cause their symptoms.

People may experience anxiety or depression after being diagnosed. The risk of suicide in cancer patients is approximately doubled.

Local symptoms

Local symptoms may occur due to tumor mass or ulceration. For example, the massive effects of lung cancer can block the bronchus, leading to coughing or pneumonia; cancer of the esophagus can cause narrowing of the esophagus, making it difficult or difficult to swallow; and colorectal cancer can lead to narrowing or blockage of the intestine, affecting bowel habits. Masses in the chest or testicles can produce noticeable lumps. An ulceration can cause bleeding, which, if it occurs in the lungs, will lead to coughing up blood, in the intestines with anemia or rectal bleeding, from the bladder with blood in the urine and in the uterus with vaginal bleeding. Although localized pain can occur with advanced cancer, the initial edema is usually painless. Some cancers can cause fluid to build up in your chest or stomach.

Systemic symptoms

Common symptoms are due to effects that are not related to direct or metastatic spread. These may include: unintended weight loss, fever, excessive fatigue, and changes in the skin. Hodgkin’s disease, leukemia, and liver or kidney cancer can cause persistent fever.

Some types of cancer can cause certain groups of systemic symptoms called paraneoplastic syndrome. Examples include the occurrence of myasthenia gravis in thymoma and tubercle in lung cancer.



Cancer can spread from its original location by local spread, lymphatic spread to regional lymph nodes, or blood-borne hematogenous spread to distant places known as metastasis. When cancer spreads through the hematogenous route, it usually spreads throughout the body. However, the “seeds” of cancer grow only in certain selected places (“soil”), as was suggested in the soil and seed hypothesis of cancer metastasis. Symptoms of metastatic cancer depend on the location of the tumor and may include enlarged lymph nodes (which can be felt or sometimes visible under the skin and which are usually hard), an enlarged liver or an enlarged spleen, which can be felt in the abdomen, pain or fracture of affected bones and neurological symptoms.


Most cancers, in 90–95% of cases, are caused by genetic mutations in environmental factors and lifestyle. The remaining 5–10% are related to hereditary genetics. The environment used by cancer researchers means any cause that is not genetically inherited, such as lifestyle, economic and behavioral factors, and not just pollution. Common environmental factors contributing to cancer death include tobacco (25–30%), diet and obesity (30–35%), infections (15–20%), radiation (both ionizing and non-ionizing, up to 10% ), lack of physical activity and environmental pollution. Psychological stress is not a risk factor for cancer. Although this may worsen the results of those who already have cancer.

As a rule, it is impossible to prove what caused a particular cancer, because various reasons do not have specific fingerprints. For example, if a person who uses tobacco develops very much lung cancer, then this was probably caused by tobacco use, but since everyone has a small chance of developing lung cancer as a result of air pollution or radiation, cancer may develop for one of those reasons. With the exception of the rare cases of transmission that occur with pregnancy and occasional organ donors, cancer is usually not transmitted.


Exposure to certain substances has been associated with specific types of cancer. These substances are called carcinogens.

For example, tobacco smoke causes 90% of lung cancer cases. It also causes cancer of the larynx, head, neck, stomach, bladder, kidney, esophagus and pancreas. Tobacco smoke contains more than fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons.

Tobacco causes one in five deaths from cancer worldwide and about one third in developed countries. Lung cancer mortality rates in the United States reflect the pattern of smoking: increased smoking has been accompanied by a sharp increase in lung cancer mortality rates, and recently there has been a decrease in smoking rates since the 1950s, followed by a decrease in lung cancer mortality rates in men since 1990 of the year. ,

In Western Europe, 10% of cancers in men and 3% of cancers in women are associated with exposure to alcohol, especially liver and gastrointestinal cancers. Cancer from exposure to work-related substances can cause 2 to 20% of cases, causing at least 200,000 deaths. Cancer, such as lung cancer and mesothelioma, can be caused by inhalation of tobacco smoke or asbestos fibers or leukemia from exposure to benzene.

Diet and exercise

Diet, lack of physical activity, and obesity are associated with 30–35% of cancer deaths. In the United States, overweight is associated with the development of many types of cancer and accounts for 14–20% of cancer deaths. A British study, including data from more than 5 million people, showed that a higher body mass index is associated with at least 10 types of cancer and causes about 12,000 cases per year in this country. It is believed that the lack of physical activity contributes to the risk of cancer not only through its effect on body weight, but also through a negative effect on the immune and endocrine systems. More than half the effect of the diet is due to excessive nutrition (overeating), and not because you eat too few vegetables or other healthy foods.

Some specific foods are associated with specific types of cancer. A high salt diet is associated with stomach cancer. Aflatoxin B1, a frequent foodborne contaminant, causes liver cancer. Betel nut chewing can cause oral cancer. National differences in dietary practices may partially explain differences in cancer incidence. For example, gastric cancer is more common in Japan due to a high-salt diet, while colon cancer is more common in the United States. Immigrant cancer profiles reflect the profiles of their new country, often within the same generation.


Worldwide, approximately 18% of cancer deaths are attributable to infectious diseases. This proportion ranges from 25% in Africa to less than 10% in developed countries. Viruses are common infectious agents that cause cancer, but cancer bacteria and parasites can also play a role.

Oncoviruses (viruses that can cause cancer) include human papillomavirus (cervical cancer), Epstein-Barr virus (B-cell lymphoproliferative disease and nasopharynx cancer), Kaposi sarcoma herpes virus (Kaposi sarcoma virus and primary effusion viruses, hepatitis B, hepatitis B (hepatitis B) hepatocellular carcinoma) and human T-cell leukemia virus-1 (T-cell leukemia). A bacterial infection can also increase the risk of developing cancer, as is the case with Helicobacter pylori-induced gastric carcinoma. Parasitic cancer-related infections include Schistosoma haematobium (squamous bladder cancer) and liver flu, Opisthorchis viverrini and Clonorchis sinensis (cholangiocarcinoma).



Radiation exposure, such as ultraviolet radiation and radioactive materials, is a risk factor for cancer. Many non-melanoma skin cancers are due to ultraviolet radiation, mainly from sunlight. Sources of ionizing radiation include medical images and radon gas.

Ionizing radiation is not a particularly strong mutagen. For example, in residential areas containing radon gas, the risk of developing cancer is similar to the risk of secondhand smoke. Radiation is a more powerful source of cancer in combination with other cancer-causing agents, such as radon plus tobacco smoke. Radiation can cause cancer in most parts of the body, in all animals and at any age. Children are twice as likely to develop radiation-induced leukemia than adults; radiation exposure before birth has a tenfold effect.

The medical use of ionizing radiation is a small but growing source of radiation-induced cancer. Ionizing radiation can be used to treat other types of cancer, but in some cases it can cause a second form of cancer. It is also used in some types of medical imaging.

Prolonged exposure to solar ultraviolet radiation can lead to melanoma and other malignant neoplasms of the skin. Obvious evidence that ultraviolet radiation, especially the non-ionizing medium-wave ultraviolet radiation, is the cause of most non-melanoma skin cancers, which are the most common forms of cancer in the world.

Non-ionizing radio frequency radiation from mobile phones, electric power transmission and other similar sources has been described by the International Agency for Research on Cancer as a possible carcinogen. Evidence, however, does not support the concern. This includes the fact that studies have not found a permanent link between mobile phone radiation and cancer risk.


The vast majority of cancers are non-hereditary (sporadic). Hereditary cancers are mainly caused by a hereditary genetic defect. Less than 0.3% of the population are carriers of a genetic mutation that has a large impact on the risk of developing cancer, and they cause less than 3-10% of cancer cases. Some of these syndromes include: certain hereditary mutations in the BRCA1 and BRCA2 genes with a greater than 75% risk of breast and ovarian cancer, as well as hereditary non-polypous colon cancer (HNPCC or Lynch syndrome), which is present in about 3% of people with colorectal cancer, among others.

Statistically for cancers causing the highest mortality, the relative risk of developing colorectal cancer when he was diagnosed with a first-degree relative (parent, brother or sister) is about 2. The corresponding relative risk is 1.5 for lung cancer and 1.9 for the prostate. cancer. For breast cancer, the relative risk is 1.8 for a first-degree relative who developed at the age of 50 and older, and 3.3 for a relative when he developed before the age of 50.

Taller people have an increased risk of developing cancer because they have more cells than shorter people. Because growth is largely genetically determined, higher people have a hereditary increase in cancer risk.

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