IRC-Galleria is the largest WWW-based virtual community in Finland. It was founded in December 2000 by Tomi Lintelä as a photo gallery for the Finnish users of Internet Relay Chat. As for February 2006, IRC-galleria boasts of over 302,000 registered users and over 3,600,000 images. About 85% of the users are active users who use the service on a weekly or daily basis. However, only about 20% of the users have identified themselves as actual users of IRC.
Despite all the features, IRC-Galleria is basically a photo gallery and it is not possible to have a user account without at least one accepted image. The maximum number of visible images per user is 60 (only for VIP-users), and the so-called default image must contain the face of the user.
The communication in IRC-Galleria is based on short messages, comments, each of which is associated with either a picture or a community. Each user can be a member of at most 40 communities. Some of the communities are named after IRC channels, and joining them requires IRC-based identification. Comments are only visible to those who are logged in.
IRC-Galleria is now maintained and developed by Dynamoid Oy, a company founded solely for the sake of IRC-Galleria. The service is financed with banner advertising, SMS-based services, T-shirts and optional VIP privileges which can be bought with SMS.
The unwillingness of the administrators of IRC-Galleria to exclude non-IRC-users has caused some schism, driving a few users to found their own alternative gallery services with a mandatory IRC-based registration. The administrators responded by introducing some features which aim at the minimization of the biggest problems related to the non-IRC-users.
The non-IRC-users registered in IRC-Galleria are sometimes ironically called galleriairkkaajat (gallery IRCers) due to the fact that many of them frequently refer to IRC-Galleria with the acronym IRC without necessarily even having a clue what the actual IRC is.
IRC-Galleria is now officially open for anyone who is over 12 years old and speaks Finnish.
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IRC-Galleria is now officially open for anyone who is over 12 years old and speaks Finnish. If cytotoxic substances (cytostatica or radionuclides) are attached to those polymers therapy of solid tumors shows promising results in some cases. The non-IRC-users registered in IRC-Galleria are sometimes ironically called galleriairkkaajat (gallery IRCers) due to the fact that many of them frequently refer to IRC-Galleria with the acronym IRC without necessarily even having a clue what the actual IRC is. Both effects together are coined the EPR (enhanced permeability and retention) effect and leads to accumulation of macromolecules within some solid tumors. The administrators responded by introducing some features which aim at the minimization of the biggest problems related to the non-IRC-users. In addition, the lymphatic drainage of tumor tissue is ineffective leading to poor clearance of substances from tumoral interstitium. The unwillingness of the administrators of IRC-Galleria to exclude non-IRC-users has caused some schism, driving a few users to found their own alternative gallery services with a mandatory IRC-based registration. Due to (often) damaged vascular structure of tumor supplying blood vessels, intravenously administered large molecules (size differs in various sources, typically M > 25 - 45 kDa, may depend on chemical structure, solubility, charge, etc.) can preferably leave the bloodstream into tumor tissue while normal blood vessels display a significant barrier for those big molecules (this is not true within glomeruli of the kidney).
The service is financed with banner advertising, SMS-based services, T-shirts and optional VIP privileges which can be bought with SMS. Another approach to target solid tumors is to apply macromolecules. IRC-Galleria is now maintained and developed by Dynamoid Oy, a company founded solely for the sake of IRC-Galleria. RGDs) eventually kill the cancer cell if the nuclide decays in the vicinity of the cell (vide supra Radiation therapy). Comments are only visible to those who are logged in. Radionuclides which are attached to this peptides (e.g. Some of the communities are named after IRC channels, and joining them requires IRC-based identification. Targeted therapy can also involve small peptidic structures as ´homing device´ which can bind to cell surface receptors or affected extracellular matrix surrounding the tumor.
Each user can be a member of at most 40 communities. Small molecules (such as the tyrosine kinase inhibitors imatinib and gefitinib) and monoclonal antibodies have proven to be a major step in oncological treatment. The communication in IRC-Galleria is based on short messages, comments, each of which is associated with either a picture or a community. This constitutes the use of agents specific for the deregulated proteins of cancer cells. The maximum number of visible images per user is 60 (only for VIP-users), and the so-called default image must contain the face of the user. Targeted therapy in the late 1990s was considered a major breakthrough. Despite all the features, IRC-Galleria is basically a photo gallery and it is not possible to have a user account without at least one accepted image. While understanding of cancer has increased exponentially since the last decades of the 20th century, radically new therapies are only discovered and introduced gradually.
However, only about 20% of the users have identified themselves as actual users of IRC. Cancer research is the intense scientific effort to understand disease processes and discover possible therapies. About 85% of the users are active users who use the service on a weekly or daily basis. Palliative care solutions may include permanent or "respite" hospice nursing. As for February 2006, IRC-galleria boasts of over 302,000 registered users and over 3,600,000 images. In the advanced stages of cancer, many patients need extensive care, affecting family members and friends. It was founded in December 2000 by Tomi Lintelä as a photo gallery for the Finnish users of Internet Relay Chat. Progressive and disseminated malignant disease has a substantial impact on a cancer patient's quality of life, and many cancer treatments (such as chemotherapy) may have severe side-effects.
IRC-Galleria is the largest WWW-based virtual community in Finland. Some types of cancer have a prognosis that is substantially better than nonmalignant diseases such as heart failure and stroke. While this certainly applies to certain particular types, the truths behind the historical connotations of cancer are increasingly being overturned by advances in medical care. Once referred to as "the C-word," cancer has a reputation for being a deadly disease. Examples include: American Cancer Society, Lance Armstrong Foundation, BC Cancer Agency, Macmillan Cancer Relief , the Terry Fox Foundation, Cancer Research UK, Canadian Cancer Society, International Agency for Research on Cancer and the National Cancer Institute (US).
These organizations often are involved in cancer prevention, cancer treatment, and cancer research. Many governmental and charitable organizations have been established to help patients cope with cancer. Different types of counseling include individual, group, family, self-help (sometimes called peer counseling), bereavement, patient-to-patient, and sexuality. Counseling can also provide emotional support to cancer patients and help them better understand their illness.
While some people are reluctant to seek counseling, studies show that having someone to talk to reduces stress and helps people both mentally and physically. Neighborhood organizations, local health care providers, or area hospitals are a good place to start looking. Support can take the form of support groups, counseling, advice, financial assistance, transportation to and from treatment, or information about cancer. Many local organizations offer a variety of practical and support services to people with cancer.
. As of October 2005, researchers found that an experimental vaccine for HPV types 16 and 18 was 100% successful at preventing infection with these types of HPV and, thus, are able to prevent the majority of cervical cancer cases. No cancer vaccines are presently in use, and most of the research is still in its initial stages. Considerable research effort is now devoted to the development of vaccines (to prevent infection by oncogenic infectious agents, as well as to mount an immune response against cancer-specific epitopes) and to potential venues for gene therapy for individuals with genetic mutations or polymorphisms that put them at high risk of cancer.
Almost all physicians recommend against using these modalities as sole treatment for potentially fatal conditions such as cancer. An extensive, explanatory catalog of these treatments is available at Quackwatch . Collectively they are referred to by skeptics as cancer quackery. Some of these treatments meet all the criteria for fraud.
Alternative treatments have included special diets or dietary supplements (e.g., the "grape diet" or megavitamin therapy), electrical devices (e.g., "zappers"), specially formulated compounds (e.g., laetrile, and homeopathic remedies), unconventional use of conventional drugs (e.g., insulin), purges or enemas, physical manipulations of the body, various herbs or herbal preparations such as essiac. Proponents of these therapies are unable or unwilling to demonstrate effectiveness by conventional criteria. The appeal of alternative cures arises from the daunting risks, costs, or potential side effects of many conventional treatments, or in the limited prospect for cure. A wide range of alternative treatments have been offered for cancer over the last century.
Other complementary approaches include traditional medicine like Traditional Chinese Medicine. Many people feel these approaches benefit them, but most have not been scientifically proven and therefore face skepticism. Common complementary measures include prayer or psychological approaches such as "imaging" or meditation to aid in pain relief, or improve mood. Some non-conventional treatment methods are used to "complement" conventional treatment, to provide comfort or lift the spirits of the patient, while others are offered as alternatives to be used instead of conventional treatments in hope of curing the cancer.
Complementary and alternative medicine (CAM) treatments are the diverse group of medical and health care systems, practices, and products that are not presently considered to be effective by the standards of conventional medicine. New treatments also may have unknown risks, but if a new treatment proves effective or more effective than standard treatment, study patients who receive it may be among the first to benefit. Of course, there is no guarantee that a new treatment being tested or a standard treatment will produce good results. They get up-to-date care from cancer experts, and they receive either a new treatment being tested or the best available standard treatment for their cancer.
Patients who take part may be helped personally by the treatment(s) they receive. Studies are done with cancer patients to find out whether promising treatments are safe and effective. Of course, treatments that work well in the lab or in animals do not always work well in people. If an approach seems promising, the next step may be testing a treatment in animals to see how it affects cancer in a living being and whether it has harmful effects.
The search for new treatments begins in the laboratory, where scientists first develop and test new ideas. A clinical trial is one of the final stages of a long and careful cancer research process. Clinical trials test many types of treatment such as new drugs, new approaches to surgery or radiation therapy, new combinations of treatments, or new methods such as gene therapy. The goal of this research is to find better ways to treat cancer and help cancer patients.
Clinical trials, also called research studies, test new treatments in people with cancer. Pain medication, such as morphine and oxycodone, and antiemetics, drugs to suppress nausea and vomiting, are very commonly used in patients with cancer-related symptoms. Although all practicing doctors have the therapeutic skills to control pain, nausea, vomiting, diarrhea, hemorrhage and other common problems in cancer patients, the multidisciplinary specialty of palliative care has arisen specifically in response to the symptom control needs of this group of patients. Although the control of the symptoms of cancer is not typically thought of as a treatment directed at the cancer, it is an important determinant of the quality of life of cancer patients, and plays an important role in the decision whether the patient is able to undergo other treatments.
Removing or blocking estrogen, testosterone, or TSH, respectively, is often an important additional treatment. Common examples of hormone-sensitive tumors include certain types of breast, prostate, and thyroid cancers. This allows an additional method of treatment for many cancers. The growth of nearly all tissues, including cancers, can be accelerated or inhibited by providing or blocking certain hormones.
These side effects include temporary (reversible) or permanent side effects (irreversible damage). Thus, as with every form of treatment, radiation therapy is not without its side effects. Radiation dose to each site depends on a number of factors, including the radiosensitivty of each cancer type and whether there are tissues and organs nearby that may be damaged by radiation. Radiation is also used to treat leukemia and lymphoma.
Radiation therapy may be used to treat almost every type of solid tumor, including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, stomach, uterus, or soft tissue sarcomas. Hence, it is given in many fractions, allowing healthy tissue to recover between fractions. The goal of radiation therapy is to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly.
In addition, they cut off the blood supply to the cancer cells causing them to die in a process called necrosis. Radiation therapy injures or destroys cells in the area being treated (the "target tissue") by damaging their genetic material, making it impossible for these cells to continue to grow and divide. The effects of radiation therapy are localised and confined to the region being treated. Radiation therapy can be administered externally via external beam radiotherapy (EBRT) or internally via brachytherapy.
Radiation therapy (also called radiotherapy, X-ray therapy, or irradiation) is the use of ionizing radiation to kill cancer cells and shrink tumors. The agents are monoclonal antibodies directed against proteins that are characteristic to the cells of the cancer in question, or cytokines that modulate the immune system's response. These are used in various forms of cancer, such as breast cancer (trastuzumab/Herceptin®) but also in leukemia (gemtuzumab ozogamicin/Mylotarg®). Immunotherapy is the use of immune mechanisms against tumors.
A variation upon this method uses allogenic samples (samples donated by a different donor) instead of the patient's own tissue. The samples are expanded using tissue engineering techniques, and are then re-implanted following high dose chemotherapy in order to recolonise the damaged and somewhat destroyed tissue. These tissues samples are screened to ensure they do not contain cancerous cells. A novel technique involves taking samples of the patient's tissue before chemotherapy.
This is called "combination chemotherapy"; most chemotherapy regimens are given in a combination. Because some drugs work better together than alone, two or more drugs are often given at the same time. These cells usually repair themselves after chemotherapy. intestinal lining).
Hence, chemotherapy has the potential to harm healthy tissue, especially those tissues that have a high replacement rate (e.g. Most forms of chemotherapy target all rapidly dividing cells and are not specific for cancer cells. with the duplication of DNA or the separation of newly formed chromosomes. It interferes with cell division in various possible ways, e.g.
Chemotherapy is the treatment of cancer with drugs ("anticancer drugs") that can destroy cancer cells. This is referred to as palliative treatment. Occasionally, surgery is necessary to control symptoms, such as spinal cord compression or bowel obstruction. Staging is a major determinant of prognosis and of the need for adjuvant therapy.
determining the extent of the disease and whether it has metastasized to regional lymph nodes. In addition to removal of the primary tumor, surgery is often necessary for staging, e.g. For this reason, the pathologist will examine the surgical specimen to determine if a margin of healthy tissue is present, thus decreasing the chance that microscopic cancer cells are left in the patient. A single cancer cell is invisible to the naked eye but can regrow into a new tumor, a process called recurrence.
The goal of the surgery can be either the removal of only the tumor, or the entire organ. Examples of surgical procedures for cancer include mastectomy for breast cancer and prostatectomy for prostate cancer. When the cancer has metastasized to other sites in the body prior to surgery, complete surgical excision is usually impossible. In theory, cancers can be cured if entirely removed by surgery, but this is not always possible.
Because "cancer" refers to a class of diseases, it is unlikely that there will ever be a single "cure for cancer" any more than there will be a single treatment for all infectious diseases. Radiation can also cause damage to normal tissue. The effectiveness of chemotherapy is often limited by toxicity to other tissues in the body. Sometimes this can be accomplished by surgery, but the propensity of cancers to invade adjacent tissue or to spread to distant sites by microscopic metastasis often limits its effectiveness.
Complete removal of the cancer without damage to the rest of the body is the goal of treatment. A number of experimental cancer treatments are also under development. The choice of therapy depends upon the location and grade of the tumor and the stage of the disease, as well as the general state of the patient (performance status). Cancer can be treated by surgery, chemotherapy, radiation therapy, immunotherapy or other methods.
Canine cancer detection has shown promise, but is still in the early stages of research. There is a significant risk of detection of what has been recently called an incidentaloma - a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations. Use of medical imaging to search for cancer in people without clear symptoms is similarly marred with problems. For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake cancer screening.
Moreover, the test itself is easy to perform and relatively cheap. Cervical cancer screening via the Pap smear has the best cost-benefit profile of all the forms of cancer screening from a public health perspective as, being a cancer, it has clear risk factors (sexual contact), and the natural progression of cervical cancer is that it normally spreads slowly over a number of years therefore giving more time for the screening program to catch it early. This is because screening of women in the general population will result in a large number of women with false positive results which require extensive follow-up investigations to exclude cancer, leading to having a high number-to-treat (or number-to-screen) to prevent or catch a single case of breast cancer early. Similarly, for breast cancer, there have recently been criticisms that breast screening programs in some countries cause more problems than they solve.
Prostate cancer treatment may cause incontinence (inability to control urine flow) and erectile dysfunction (erections inadequate for intercourse). Follow up procedures used to diagnose prostate cancer (prostate biopsy) may cause side effects, including bleeding and infection. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. For example: when screening for prostate cancer, the PSA test may detect small cancers that would never become life threatening, but once detected will lead to treatment.
The controversy arises when it is not clear if the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments. Screening for cancer is controversial in cases when it is not yet known if the test actually saves lives. Prostate cancer can be screened for by a digital rectal exam along with prostate specific antigen (PSA) blood testing. Testicular self-examination is recommended for men beginning at the age of 15 years to detect testicular cancer.
Over time, such testing has been followed by a dramatic reduction of cervical cancer incidence and mortality. Similarly, cervical cytology testing (using the Pap smear) leads to the identification and excision of precancerous lesions. Colorectal cancer can be detected through fecal occult blood testing and colonoscopy, which reduces both colon cancer incidence and mortality, presumably through the detection and removal of premalignant polyps. Screening by regular mammograms detects tumors even earlier than self-examination, and many countries use it to systematically screen all middle-aged women.
Breast cancer screening can be done by breast self-examination. A number of different screening tests have been developed. Early diagnosis may lead to extended life. Screening for cancer can lead to earlier diagnosis.
If signs of cancer are detected, more definitive and invasive follow up tests are performed to confirm the diagnosis. Screening tests suitable for large numbers of healthy people must be relatively affordable, safe, noninvasive procedures with acceptably low rates of false positive results. Cancer screening is an attempt to detect unsuspected cancers in the population. Cytogenetics and immunohistochemistry may provide information about future behavior of the cancer (prognosis) and best treatment.
Together, this information is useful to evaluate the prognosis of this patient and choose the best treatment. The tissue diagnosis indicates the type of cell that is proliferating, its histological grade and other features of the tumor. Biopsies of other organs are performed under anesthesia and require surgery in an operating room. Many biopsies (such as those of the skin, breast or liver) can be done in a doctor's office.
Tissue can be obtained from a biopsy or surgery. A cancer may be suspected for a variety of reasons, but the definitive diagnosis of most malignancies must be confirmed by histological examination of the cancerous cells by a pathologist. Cancer may be a common or uncommon cause of each item. Every single item in the above list can be caused by a variety of conditions (a list of which is referred to as the differential diagnosis).
Roughly, cancer symptoms can be divided into three groups:. Neither of these lead to a definitive diagnosis, which usually requires the opinion of a pathologist. Most cancers are initially recognized either because signs or symptoms appear or through screening. Genetic testing for high-risk individuals, with enhanced surveillance, chemoprevention, or risk-reducing surgery for those who test positive, is already available for certain cancer-related genetic mutations.
Other examples of drugs that show promise for chemoprevention include COX-2 inhibitors (which inhibit a cyclooxygenase enzyme involved in the synthesis of proinflammatory prostaglandins). Finasteride, a 5-alpha reductase inhibitor, has been shown to lower the risk of prostate cancer. Cis-retinoic acid also has been shown to reduce risk of second primary tumors among patients with primary head and neck cancer. Daily use of tamoxifen, a selective estrogen receptor modulator, for up to 5 years, has been demonstrated to reduce the risk of developing breast cancer in high-risk women by about 50%.
In fact, the risk of lung cancer was slightly, but not significantly, increased by beta-carotene, leading to an early termination of the study. Contrary to expectation, these tests found no benefit of beta-carotene supplementation in reducing lung cancer incidence and mortality. This study provided about 80,000 smokers or former smokers with daily supplements of beta-carotene or placebos. This hypothesis led to a series of large randomized trials conducted in both Finland and the United States (CARET study) during the 1980s and 1990s.
This effect was particularly strong in lung cancer. Epidemiologists studying both diet and serum levels observed that high levels of beta-carotene, a precursor to vitamin A, were associated with a protective effect, reducing the risk of cancer. The case of beta-carotene provides an example of the necessity of randomized clinical trials. Public health recommendations cannot be made on the basis of these studies until they have been validated in an observational (or occasionally a prospective interventional) trial in humans.
These reports are often based on studies in cultured cell media or animals. Despite frequent reports of particular substances (including foods) having a beneficial or detrimental effect on cancer risk, few of these have an established link to cancer. Studies have shown that immigrants develop the risk of their new country, suggesting a link between diet and cancer rather than a genetic basis. gastric cancer is more common in Japan, while colon cancer is more common in the United States).
Particular dietary practices often explain differences in cancer incidence in different countries (e.g. The consensus on diet and cancer is that obesity increases the risk of developing cancer. Other lifestyle and environmental factors known to affect cancer risk (either beneficially or detrimentally) include certain sexual and reproductive practices, the use of exogenous hormones, exposure to ionizing radiation and ultraviolet radiation, certain occupational and chemical exposures, and infectious agents. Based on epidemiologic evidence, it is now thought that avoiding excessive alcohol consumption, being physically active, and maintaining recommended body weight may all contribute to reductions in risk of certain cancers; however, compared with tobacco exposure, the magnitude of effect is modest or small and the strength of evidence is often weaker.
Examples of modifiable cancer risk include alcohol consumption (associated with increased risk of oral, esophageal, breast, and other cancers), physical inactivity (associated with increased risk of colon, breast, and possibly other cancers), and being overweight (associated with colon, breast, endometrial, and possibly other cancers). Evidence is now emerging from randomized controlled trials designed to test whether interventions suggested by the epidemiologic studies, as well as leads based on laboratory research, actually result in reduced cancer incidence and mortality. Much of the promise for cancer prevention comes from observational epidemiologic studies that show associations between modifiable life style factors or environmental exposures and specific cancers. This can be accomplished by avoiding carcinogens or altering their metabolism, pursuing a lifestyle or diet that modifies cancer-causing factors and/or medical intervention (chemoprevention, treatment of premalignant lesions).
Cancer prevention is defined as active measures to decrease the incidence of cancer. Similarly, with tobacco smoking becoming more common in various Third World countries, lung cancer incidence has increased in a parallel fashion. Hepatocellular carcinoma (liver cancer) is rare in the West but is the main cancer in China and neighboring countries, most likely due to the endemic presence of hepatitis B and aflatoxin in that population. Cancer epidemiology closely mirrors risk factor spread in various countries.
With the increased control over malaria and tuberculosis in some Third World countries, incidence of cancer is expected to rise; this is termed the iceberg phenomenon in epidemiological terminology. In many Third World countries cancer incidence (insofar as this can be measured) appears much lower, most likely because of the higher death rates due to infectious disease or injury. In some Western countries, such as the USA and the UK, cancer is overtaking cardiovascular disease as the leading cause of death. Up to half of all cancer cases can be attributed to smoking, diet, and environmental pollution.
Further support comes from the fact that lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking followed by decreases in lung cancer death rates in men. Hundreds of epidemiological studies have confirmed this association. The most consistent finding, over decades of research, is the strong association between tobacco use and cancers of many sites. Examples are:.
There are, however, a number of recognised syndromes of cancer with a hereditary component. Most forms of cancer are "sporadic", and have no basis in heredity. Nevertheless, carcinoma in situ may develop into an invasive malignancy and is usually removed surgically, if possible. The most severe cases of dysplasia are referred to as "carcinoma in situ." In Latin, the term "in situ" means "in place", so carcinoma in situ refers to an uncontrolled growth of cells that remains in the original location and shows no propensity to invade other tissues.
Often such cells revert back to normal behavior, but occasionally, they gradually become malignant. Dysplasia is an abnormal type of excessive cell proliferation characterized by loss of normal tissue arrangement and cell structure. Hyperplasia can be a normal tissue response to an irritating stimulus, for example callus. This process is considered reversible.
Biopsy and microscopical examination can also distinguish between malignancy and hyperplasia, which refers to tissue growth based on an excessive rate of cell division, leading to a larger than usual number of cells but with a normal orderly arrangement of cells within the tissue. Immunohistochemistry and other molecular methods may characterise specific markers on tumor cells, which may aid in diagnosis and prognosis. Among the distinguishing traits are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary. Cancer tissue has a distinctive appearance under the microscope.
Cells that divide at a high rate, such as epithelials, show a higher risk of becoming tumor cells than those which divide less, for example neurons. Also, the DNA methylation pattern of the cell changes, activating and deactivating genes without the usual regulation. The instability can increase to a point where the cell loses whole chromosomes, or has multiple copies of several. A first step in the development of a tumor cell is usually a small change in the DNA, often a point mutation, which leads to a genetic instability of the cell.
This process is called clonal evolution. A cell that degenerates into a tumor cell does not usually acquire all these properties at once, but its descendant cells are selected to build them.
Telomerase mutations remove additional barriers, extending the number of times a cell can divide. This mutation is associated with poor prognosis, since those tumor cells are less likely to go into apoptosis or programmed cell death when damaged by therapy. For example, up to half of all tumors have a defective p53 gene. However, with the help of molecular biological techniques, it is possible to characterize the mutations or chromosomal aberrations within a tumor, and rapid progress is being made in the field of predicting prognosis based on the spectrum of mutations in some cases.
It is impossible to tell the initial cause for any specific cancer. Because viral genome insertion is not specific to proto-oncogenes and the chance of insertion near that proto-oncogene is low, slowly-transforming viruses have very long tumor latency compared to acutely-transforming viruses, which already carry the viral-oncogene. The viral promoter or other transcription regulation elements in turn cause overexpression of that proto-oncogene, which in turn induces uncontrolled cellular proliferation. In contrast, in slowly-transforming viruses, the virus genome is inserted, especially as viral genome insertion is an obligatory part of retroviruses, near a proto-oncogene in the host genome.
In acutely transforming viruses, the viral particles carry a gene that encodes for an overactive oncogene called viral-oncogene (v-onc), and the infected cell is transformed as soon as v-onc is expressed. The mode of virally-induced tumors can be divided into two, acutely-transforming or slowly-transforming. Furthermore, many cancers originate from a viral infection; this is especially true in animals such as birds, but less so in humans, as viruses are only responsible for 15% of human cancers. A mistake made during mitosis can lead to the daughter cells receiving the wrong number of chromosomes, which leads to aneuploidy and may lead to cancer.
Faster rates of mitosis increasingly leave less opportunities for repair enzymes to repair damaged DNA during DNA replication, increasingly the likelihood of a genetic mistake. These are thought to promote cancers through their stimulating effect on the rate of cell mitosis. Examples of carcinogens that are not mutagens include alcohol and estrogen. Many mutagens are also carcinogens, but some carcinogens are not mutagens.
Chromosomal translocations, such as the Philadelphia chromosome, are a special type of mutation that involve exchanges between different chromosomes. Other types of mutations can be caused by chronic inflammation, as neutrophil granulocytes secrete free radicals that damage DNA. In more general terms, chemicals called mutagens and free radicals are known to cause mutations. Breathing asbestos fibers is associated with mesothelioma.
Prolonged exposure to radiation, particularly ultraviolet radiation from the sun, leads to melanoma and other skin malignancies. Tobacco smoking is associated with lung cancer. Particular substances have been linked to specific types of cancer. Substances that cause these mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens.
Cancer is ultimately due to accumulation of genetic damage, which are fundamentally mutations in the DNA. Similarly, mutations in the adenomatous polyposis coli gene are linked to adenopolyposis colon cancer, with thousands of polyps in colon while young, while mutations in BRCA1 and BRCA2 lead to early onset of breast cancer. For instance, individuals who are heterozygous for p53 mutations are often victims of Li-Fraumeni syndrome, and those who are heterozygous for Rb mutations develop retinoblastoma. Because mutations in tumor suppressers act in a recessive manner (note, however, there are exceptions), the loss of the normal copy creates the cancer phenotype.
The mode of inheritance of mutant tumor suppressors is that affected member inherits a defective copy from one parent, and a normal copy from another. Members within these families have increased incidence and decreased latency of multiple tumors. Mutation of tumor suppressor genes that are passed on to the next generation of not merely cells, but their offspring can cause increased likelihoods for cancers to be inherited. This is observed in many p53 mutations.
However, cases exist in which one loss of function copy of a tumor suppressor gene can render the other copy non-functional, and this is called dominant negative effect. Each cell has two copies of a same gene, one from each parent, and under most cases gain of function mutation in one copy of a particular proto-oncogene is enough to make that gene a true oncogene, while usually loss of function mutation need to happen in both copies of a tumor suppressor gene to render that gene completely non-functional. Usually, oncogenes are dominant, as they contain gain of function mutations, while mutated tumor suppressors are recessive, as they contain loss of function mutations. Often, because these genes regulate the processes that prevent most damage to genes themselves, the rate of mutations increase as one gets older, because DNA damage forms a feedback loop.
It is only when enough proto-oncogenes have mutated into oncogenes, and enough tumor suppressor genes deactivated or damaged, that the signals for cell growth overwhelm the signals to regulate it, that cell growth quickly spirals out of control. A mutation to only one tumor suppressor gene would not cause cancer either, due to the presence of many "backup" genes that duplicate its functions. For example, a mutation limited to one oncogene would be suppressed by normal mitosis control and tumor suppressor genes, which was first hypothesised by the Knudson hypothesis. In general, mutations in both types of genes are required for cancer to occur.
The invariable consequence of this is that DNA repair is hindered or inhibited: DNA damage accumulates without repair, inevitably leading to cancer. However, a mutation can damage the tumor suppressor gene itself, or the signal pathway which activates it, "switching it off". Canonical tumor suppressors include the p53 gene, which is a transcription factor activated by many cellular stressors including hypoxia and ultraviolet radiation damage. The functions of such genes is to arrest the progression of cell cycle in order to carry out DNA repair, preventing mutations from being passed on to daughter cells.
Often DNA damage will cause the presence of free-floating genetic material as well as other signs, and will trigger enzymes and pathways which lead to the activation of tumor suppressor genes. Generally tumor suppressors are transcription factors that are activated by cellular stress or DNA damage. Tumor suppressor genes code for anti-proliferation signals and proteins that suppress mitosis and cell growth. It is only when they become mutated, that the signals for growth become excessive.
The chance of cancer cannot be reduced by removing proto-oncogenes from the genome as they are critical for growth, repair and homeostasis of the body. When this happens, they become oncogenes, and thus cells have a higher chance to divide excessively and uncontrollably. Mutations in proto-oncogenes can modify their function, increasing the amount or activity of the product protein. They often produce mitogens, or are involved in transcription of DNA in protein synthesis, which create the proteins and enzymes is responsible for producing the products and biochemicals cells use and interact with.
Some are responsible for the signal transduction system and signal receptors in cells and tissues themselves, thus controlling the sensitivity to such hormones. Many can produce hormones, a "chemical messenger" between cells which encourage mitosis, the effect of which depends on the signal transduction of the receiving tissue or cells. Proto-oncogenes, promote cell growth through a variety of ways. Typically, a series of several mutations to these genes are required before a normal cell transforms into a cancer cell.
Proto-oncogenes are genes which promote cell growth and mitosis, a process of cell division, and tumor suppressor genes discourage cell growth, or temporarily halts cell division from occurring in order to carry out DNA repair. In order for cells to start dividing uncontrollably, genes which regulate cell growth must be damaged. Cancer is, ultimately, a disease of genes. Carcinogenesis (meaning literally, the creation of cancer) is the process of derangement of the rate of cell division due to damage to DNA.
Malignant tumors can invade other organs, spread to distant locations (metastasize) and become life-threatening. Benign tumors do not spread to other parts of the body or invade other tissues, and they are rarely a threat to life unless they extrinsically compress vital structures. The uncontrolled and often rapid proliferation of cells can lead to either a benign tumor or a malignant tumor (cancer). Mutations in DNA that lead to cancer disrupt these orderly processes.
Normally the balance between proliferation and cell death is tightly regulated to ensure the integrity of organs and tissues. Cell division (proliferation) is a physiological process that occurs in almost all tissues and under many circumstances. Relative survival for infants is very good for neuroblastoma, Wilms' tumor and retinoblastoma, and fairly good (80%) for leukemia, but not for most other types of cancer. Female infants and male infants have essentially the same overall cancer incidence rates, but white infants have substantially higher cancer rates than black infants for most cancer types.
The remainder consists of Wilms' tumor, lymphomas, rhabdomyosarcoma (arising from muscle), retinoblastoma, osteosarcoma and Ewing's sarcoma. Leukemia (usually ALL) is the most common infant malignancy (30%), followed by the central nervous system cancers and neuroblastoma. The age of peak incidence of cancer in children occurs during the first year of life. Cancer can also occur in young children and adolescents, but it is rare.
These statistics vary substantially in other countries. The statistics below are for adults in the United States. On a yearly basis, 0.5% of the population is diagnosed with cancer. In the USA and other developed countries, cancer is presently responsible for about 25% of all deaths.
neuroblastoma and lymphoma. This nomenclature is however somewhat inconsistent, since several "malignant" tumor growths also have this suffix in their names, e.g. For instance, a benign tumor of the smooth muscle of the uterus is called leiomyoma (the common name of this frequent tumor is fibroid). Benign tumors are named using -oma as a suffix.
Here, the adjective ductal refers to the appearance of the cancer under the microscope, resembling normal breast ducts. For instance, the most common type of breast cancer is called ductal carcinoma of the breast or mammary ductal carcinoma. For common cancers, the English organ name is used. For instance, a malignant tumor of liver cells is called hepatocarcinoma; a malignant tumor of the fat cells is called liposarcoma.
Malignant tumors are usually named using the Latin or Greek root of the organ as a prefix and the above category name as the suffix. The following general categories are usually accepted:. Cancers are classified by the type of cell that resembles the tumor and, therefore, the tissue presumed to be the origin of the tumor. The following closely related terms may be used to designate abnormal growths:.
Galen used "oncos" to describe all tumours, the root for the modern word oncology.. It is Celsus who translated carcinos into the latin cancer, also meaning crab. Today, carcinoma is the medical term for a malignant tumour derived from epithelial cells. He later added the suffix -oma, Greek for swelling, giving the name carcinoma.
This strange choice of name probably comes from the appearance of the cut surface of a solid malignant tumour, with a roundish hard center surrounded by pointy projections, vaguely resembling the silhouette of a crab. He called benign tumours oncos, Greek for swelling, and malignant tumours carcinos, Greek for crab or crayfish. Hippocrates described several kinds of cancers. .
Some of these can be avoidable, and public health and vaccination programmes are important on a global scale. Many forms of cancer are associated with exposure to environmental factors, such as tobacco smoking, alcohol, and certain viruses. Most cancers can be treated and many cured, especially if treatment begins early. Cancer is mainly a disease of later years, and is one of the leading causes of death in developed countries.
If untreated, cancers may eventually cause death. Once diagnosed, cancer is usually treated with surgery, chemotherapy, or radiation. This tissue is obtained by biopsy or surgery. A definitive diagnosis usually requires the histologic examination of tissue by a pathologist.
Cancer may be painless. Cancer can cause many different symptoms, depending on the site and character of the malignancy and whether there is metastasis. Some mutations occur spontaneously, or they can be inherited (germ line mutations.). These mutations are often caused by chemicals or physical agents called carcinogens.
Several mutations may be required to transform a normal cell into a malignant cell. This unregulated growth is caused by damage to DNA, resulting in mutations to genes that control cell division. Cancer is a class of diseases characterized by uncontrolled division of cells and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by implantation into distant sites (metastasis). specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.
Systemic symptoms: weight loss, poor appetite and cachexia (wasting), excessive sweating (night sweats), anemia and specific paraneoplastic phenomena, i.e. Although advanced cancer may cause pain, it is often not the first symptom. Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Compression of surrounding tissues may cause symptoms such as jaundice.
Local symptoms: unusual lumps or swelling (tumor), hemorrhage (bleeding), pain and/or ulceration. Retinoblastoma in young children is an inherited cancer. Familial adenomatous polyposis an inherited mutation of the APC gene that leads to early onset of colon carcinoma. Turcot syndrome (brain tumors and colonic polyposis).
Li-Fraumeni syndrome (various tumors such as osteosarcoma, breast cancer, soft-tissue sarcoma, brain tumors) due to mutations of p53. tumors of various endocrine organs in multiple endocrine neoplasia (MEN types 1, 2a, 2b). certain inherited mutations in the genes BRCA1 and BRCA2 are associated with an elevated risk of breast cancer and ovarian cancer. ability to promote blood vessel growth (angiogenesis).
ability to build metastases at distant sites. ability to invade neighbouring tissues. no ability for contact inhibition. altered ability to differentiate.
increased cell division rate. insensitivity to anti-growth factors. self-sufficiency of growth factors. unlimited growth potential (immortalitization) due to overabundance of telomerase.
evading apoptosis. Choriocarcinoma: malignant tumors derived from the placenta. germ cell tumours: tumors derived from germ cells, normally found in the testicle and ovary. Glioma: tumors derived from brain cells.
Mesothelioma: tumors derived from the mesothelial cells lining the peritoneum and the pleura. Sarcoma: malignant tumors derived from connective tissue, or mesenchymal cells. Lymphoma and Leukemia: malignant tumors derived from blood and bone marrow cells. This group represent the most common cancers, including the common forms of breast, prostate, lung and colon cancer.
Carcinoma: malignant tumors derived from epithelial cells. This is inaccurate since some neoplasms usually do not form tumors, for example leukemia or carcinoma in situ. In common language, however, it is synonymous with 'neoplasm', either benign or malignant. Tumor in medical language simply means swelling or lump, either neoplastic, inflammatory or other.
Because of its overwhelming popularity relative to 'neoplasia', it is used frequently instead of 'neoplasia', even by scientists and physicians, especially when discussing neoplastic diseases as a group. Occasionally, it is used instead of carcinoma, a sub-group of malignant neoplasms. Cancer is a widely used word that is usually understood as synonymous with malignant neoplasm. Neoplasms can be benign or malignant.
This group contains a large number of different diseases; the usual classification is listed below. Neoplasia and neoplasm are the accurate, scientific names for this group of diseases as defined in the first paragraph above.