Causes of Cancer
Cancer Causes: Book Excerpts
Cancer as a complication of other conditions:
Other conditions that might have
Cancer as a complication may,
potentially, be an underlying cause of Cancer.
Our database lists the following as having
Cancer as a complication of that condition:
Cancer as a symptom:
Conditions listing Cancer
as a symptom may also be potential underlying causes of Cancer.
Our database lists the following as having
Cancer as a symptom of that condition:
What causes Cancer?
Causes: Cancer:
There are many possible causes of cancer.
See also articles
Cancer Theories,
or Cancer Causes.
Cancer occurs when cell division gets out of control. Usually, the timing of cell division is under strict constraint, involving a network of signals that work together to say when a cell can divide, how often it should happen and how errors can be fixed.
(Source: Genes and Disease by the National Center for Biotechnology)
Article excerpts about the
causes of Cancer:
What You Need To Know About Cancer - An Overview: NCI (Excerpt)
The body is made up of many types of cells. Normally, cells
grow and divide to produce more cells only when the body needs
them. This orderly process helps keep the body healthy.
Sometimes, however, cells keep dividing when new cells are not
needed. These extra cells form a mass of tissue ,
called a growth or tumor . (Source: excerpt from What You Need To Know About Cancer - An Overview: NCI)
What You Need To Know About Cancer - An Overview: NCI (Excerpt)
Even though doctors can seldom explain why one person gets
cancer and another does not, it is clear that cancer is not
caused by an injury, such as a bump or bruise. And although
being infected with certain viruses may increase the risk of
some types of cancer, cancer is not contagious; no one can
"catch" cancer from another person.
Cancer develops over time. It is a result of a complex mix
of factors related to lifestyle, heredity, and environment. A
number of factors that increase a person's chance of
developing cancer have been identified. Many types of cancer
are related to the use of tobacco, what people eat and drink,
exposure to ultraviolet
(UV) radiation from the sun, and, to a lesser extent,
exposure to cancer-causing agents (carcinogens )
in the environment and the workplace. Some people are more
sensitive than others to factors that can cause cancer. (Source: excerpt from What You Need To Know About Cancer - An Overview: NCI)
Medical news summaries relating to Cancer:
The following medical news items are relevant to causes of Cancer:
Cause statistics for Cancer:
The following are statistics from various sources about the causes of Cancer:
- Cancer was the underlying cause in 88.6% of cancer deaths in Australia 2002 (AIHW & AACR, 2003, Australia’s Health 2004, AIHW)
- Cancer was the underlying cause in 90.2% of female deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Cancer was the underlying cause in 88.0% of male deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Coronary heart disease was an underlying cause in 4.6% of female deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Coronary Heart Disease was an underlying cause in 7.5% of male deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Endocrine disease was an underlying cause in 13.6% of female deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Endocrine disease was an underlying cause in 17.7% of male deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Respiratory disease was an underlying cause in 12.4% of female deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Respiratory disease was an underlying cause in 15.7% of male deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Stroke was an underlying cause in 4.7% of female deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- Stroke was an underlying cause in 8.2% of male deaths from cancer in Australia 1997-2002 (AIHW National Morbidity Database, Australia’s Health 2004, AIHW)
- 1,227 deaths from cancer were caused directly by alcohol consumption in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 7,650 deaths from cancer was caused directly by smoking in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 6.5 per 100,000 population of deaths from cancer were caused directly by alcohol consumption in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 40.5 per 100,000 population died from cancer caused directly by smoking in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- Cancer was the associated cause of death in 11.4% of cancer deaths in Australia 2002 (AIHW & AACR, 2003, Australia’s Health 2004, AIHW)
- Cancer was the associated cause of death in 4,826 cancer deaths in Australia 2002 (AIHW & AACR, 2003, Australia’s Health 2004, AIHW)
- Smoking accounts for an estimated 16.8% of new cases of cancer in men in Australia (AACR, 2003, Australia’s Health 2004, AIHW)
- Smoking accounts for an estimated 7.9% of new cases of cancer in women in Australia (AACR, 2003, Australia’s Health 2004, AIHW)
- 10,807 new cases of cancer was caused directly by smoking in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 14.3 per 100,000 population of new cases of cancer were caused directly by alcohol consumption in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 2,697 new cases of cancer were caused directly by alcohol consumption in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- 57.2 per 100,000 population of new cases of cancer was caused directly by smoking in Australia 2000 (AACR, 2003, Australia’s Health 2004, AIHW)
- more statistics...»
Related information on causes of Cancer:
As with all medical conditions,
there may be many causal factors.
Further relevant information on causes of Cancer may be found in:
Causes of Cancer: Online Medical Books
16 MEDICAL BOOKS ONLINE!
Review excerpts from medical books online, free, without registration,
for more information about the causes of Cancer.
Breast cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The cause of breast cancer isn't known, but its high incidence in women implicates estrogen.
Certain predisposing factors are clear; women at high risk include those who have a family history of breast cancer, particularly first-degree relatives (mother, sister, and maternal aunt).
Other women at high risk include those who:
❑have long menstrual cycles or began menses early (before age 12) or menopause late (after age 55)
❑have taken hormonal contraceptives
❑used hormone replacement therapy for more than 5 years
❑who took diethylstilbestrol to prevent miscarriage
❑have never been pregnant
❑were first pregnant after age 30
❑have had unilateral breast cancer
❑have had ovarian cancer — particularly at a young age
❑were exposed to low-level ionizing radiation.
Recently, scientists have discovered the BRCA1 and BRCA2 genes. Mutations in these genes are thought to be responsible for less than 10% of breast cancers. However, these discoveries have made genetic predisposition testing an option for women at high risk for breast cancer.
Women at lower risk include those who:
❑were pregnant before age 20
❑have had multiple pregnancies
❑are Native American or Asian.
Most breast cancer deaths occur in women age 50 and older (84% of cases), and 77% of new breast cancer cases occur in this age-group. However, it may develop any time after puberty. It occurs in men, but rarely; male cases of breast cancer account for less than 1% of all cases.
The 5-year survival rate for localized breast cancer has improved because of earlier diagnosis and the variety of treatments now available. According to the most recent data, mortality rates continue to decline in White women and, for the first time, are also declining in younger Black women. Lymph node involvement is the most valuable prognostic predictor. With adjuvant therapy, 70% to 75% of women with negative nodes will survive 10 years or more compared with 20% to 25% of women with positive nodes.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Introduction: Malignant Neoplasms:
What causes cancer?
(Professional Guide to Diseases (Eighth Edition))
Researchers have found that cancer develops from mutations within the genes of cells. Thus, cancer is a genetic disease. Cancer susceptibility genes are of two types. Some are oncogenes, which activate cell division and influence embryonic development, and some are tumor suppressor genes, which halt cell division.
These genes are typically found in normal human cells, but certain kinds of mutations may transform the normal cells. Inherited defects may cause a genetic mutation, whereas exposure to a carcinogen may cause an acquired mutation. Current evidence indicates that carcinogenesis results from a complex interaction of carcinogens and accumulated mutations in several genes.
In animal studies of the ability of viruses to transform cells, some human viruses exhibit carcinogenic potential. For example, the Epstein-Barr virus, the cause of infectious mononucleosis, has been linked to Burkitt's lymphoma and nasopharyngeal cancer.
High-frequency radiation, such as ultraviolet and ionizing radiation, damages the genetic material known as deoxyribonucleic acid (DNA), possibly inducing genetically transferable abnormalities. Other factors, such as a person's tissue type and hormonal status, interact to potentiate radiation's carcinogenic effect. Examples of substances that may damage DNA and induce carcinogenesis include:
❑alkylating agents — leukemia
❑aromatic hydrocarbons and benzopyrene (from polluted air) — lung cancer
❑asbestos — mesothelioma of the lung
❑tobacco — cancer of the lung, oral cavity and upper airways, esophagus, pancreas, kidneys, and bladder
❑vinyl chloride — angiosarcoma of the liver.
Diet has also been implicated, especially in the development of GI cancer as a result of a high animal fat diet. Additives composed of nitrates and certain methods of food preparation — particularly charbroiling — are also recognized factors.
The role of hormones in carcinogenesis is still controversial, but it seems that excessive use of some hormones, especially estrogen, produces cancer in animals. Also, the synthetic estrogen diethylstilbestrol causes vaginal cancer in some daughters of women who were treated with it. It's unclear, however, whether changes in human hormonal balance retard or stimulate cancer development.
Some forms of cancer and precancerous lesions result from genetic predisposition either directly (as in Wilms' tumor and retinoblastoma) or indirectly (in association with inherited conditions such as Down syndrome or immunodeficiency diseases). Expressed as autosomal recessive, X-linked, or autosomal dominant disorders, their common characteristics include:
❑early onset of malignant disease
❑increased incidence of bilateral cancer in paired organs (breasts, adrenal glands, kidneys, and eighth cranial nerve [acoustic neuroma])
❑increased incidence of multiple primary malignancies in nonpaired organs
❑abnormal chromosome complement in tumor cells.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Malignant spinal neoplasms:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Primary tumors of the spinal cord may be extramedullary (occurring outside the spinal cord) or intramedullary (occurring within the cord itself). Extramedullary tumors may be intradural (meningiomas and schwannomas), which account for 60% of all primary malignant spinal cord neoplasms, or extradural (metastatic tumors from breasts, lungs, prostate, leukemia, or lymphomas), which account for 25% of these malignant neoplasms.
Intramedullary tumors, or gliomas (astrocytomas or ependymomas), are comparatively rare, accounting for only about 10%. In children, they're low-grade astrocytomas.
Spinal cord tumors are rare compared with intracranial tumors (ratio of 1:4). They occur equally in men and women, with the exception of meningiomas, which occur mostly in women. Spinal cord tumors can occur anywhere along the length of the cord or its roots.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Bladder cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Certain environmental carcinogens, such as 2-naphthylamine, benzidine, tobacco, and nitrates, predispose people to transitional cell tumors. Thus, workers in certain industries (rubber workers, weavers and leather finishers, aniline dye workers, hair-dressers, petroleum workers, and spray painters) are at high risk for such tumors. The period between exposure to the carcinogen and development of symptoms is about 18 years.
Squamous cell cancer of the bladder is most common in geographic areas where schistosomiasis is endemic. It's also associated with chronic bladder irritation and infection (for example, from renal calculi, indwelling urinary catheters, and cystitis caused by cyclophosphamide).
Bladder tumors are most prevalent in men older than age 50 and are more common in densely populated industrial areas.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Cancer of the vulva:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Although the cause of cancer of the vulva is unknown, several factors seem to predispose women to this disease:
❑chronic pruritus of the vulva, with friction, swelling, and dryness
❑ chronic vulvar granulomatous disease
❑ diabetes
❑ hypertension
❑ irradiation of the skin such as nonspecific treatment for pelvic cancer
❑ leukoplakia (white epithelial hyperplasia) — in about 25% of patients
❑ obesity
❑ pigmented moles that are constantly irritated by clothing or perineal pads
❑ sexually transmitted diseases (herpes simplex, condyloma acuminatum caused by human papilloma virus).
Cancer of the vulva accounts for approximately 4% of all gynecologic malignancies. It can occur at any age, even in infants, but its peak incidence is in the mid-60s. The most common vulval cancer is squamous cell cancer. Early diagnosis increases the chance of effective treatment and survival. Lymph node dissection allows 5-year survival in 85% of patients if it reveals no positive nodes; otherwise, the survival rate falls to less than 75%.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Cervical cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Although the cause is unknown, several predisposing factors have been related to the development of cervical cancer: frequent intercourse at a young age (younger than age 16), multiple sexual partners, multiple pregnancies, exposure to sexually transmitted diseases (particularly genital human papillomavirus), and smoking.
In almost all cases of cervical cancer (95%), the histologic type is squamous cell cancer, which varies from well-differentiated cells to highly anaplastic spindle cells. Only 5% are adenocarcinomas. Usually, invasive cancer occurs between ages 30 and 50; rarely, in patients younger than age 20.
In 2000, 12,800 women were diagnosed with cervical cancer and there were 4,600 deaths from this disease.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Colorectal cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The exact cause of colorectal cancer is unknown, but studies showing concentration in areas of higher economic development suggest a relationship to diet (excess saturated animal fat). Other factors that magnify the risk of developing colorectal cancer include:
❑other diseases of the digestive tract
❑age (older than age 40)
❑history of ulcerative colitis (average interval before onset of cancer is 11 to 17 years)
❑familial polyposis (cancer almost always develops by age 50).
There are more than 130,000 cases of colorectal cancer diagnosed in the United States each year. It's the second-leading cause of cancer-related death, accounting for more than 50,000 per year. However, in almost all cases, it's treatable if caught early by colonoscopy.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Esophageal cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The cause of esophageal cancer is unknown, but among predisposing factors are chronic irritation caused by heavy smoking and excessive use of alcohol, stasis-induced inflammation, nutritional deficiency, and diets high in nitrosamines. A genetic link has been proposed concerning an overexpression and mutation of the p53 tumor suppressor gene. Esophageal tumors are usually fungating and infiltrating. Most arise in squamous cell epithelium. However, the number of adenocarcinomas is greatly rising in the United States. Melanomas and sarcomas are few.
Regardless of type, esophageal cancer is usually fatal, with a 5-year survival rate of approximately 10% and regional metastasis occurring early via submucosal lymphatics. Metastasis produces such serious complications as tracheoesophageal fistulas, mediastinitis, and aortic perforation. Common sites of distant metastasis include the liver and lungs. (See Staging esophageal cancer.)
Esophageal cancer most commonly develops in men older than age 60 and is nearly always fatal. This disease occurs worldwide, but incidence varies geographically. It's most common in Japan, China, the Middle East, and parts of South Africa.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Fallopian tube cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The causes of fallopian tube cancer aren't clear, but this disease appears to be linked with nulliparity. In fact, over one-half of the women with this disease have never had children.
Fallopian tube cancer usually occurs in postmenopausal women in their 50s and 60s but occasionally is found in younger women.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Gallbladder and bile duct cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Gallbladder cancer may result from a complication of gallstones. However, this inference rests on circumstantial evidence from postmortem examinations: 60% to 90% of gallbladder cancer patients also have gallstones, but postmortem data from patients with gallstones show gallbladder cancer in only 0.5%.
The predominant tissue type in gallbladder cancer is adenocarcinoma, 85% to 95%; squamous cell, 5% to 15%. Mixed-tissue types are rare.
Lymph node metastasis is present in 25% to 70% of patients at diagnosis. Direct extension to the liver is common (in 46% to 89%); direct extension to both the cystic and the common bile ducts, stomach, colon, duodenum, and jejunum also occurs and produces obstructions. Metastasis also spreads by portal or hepatic veins to the peritoneum, ovaries, and lower lung lobes.
The cause of extrahepatic bile duct cancer isn't known; however, statistics report an unexplained increased incidence of this cancer in patients with ulcerative colitis. This association may be due to a common cause — perhaps an immune mechanism, or chronic use of certain drugs by the colitis patient.
Extrahepatic bile duct cancer is the cause of approximately 3% of all cancer deaths in the United States. It occurs in both males and females (incidence is slightly higher in males) between ages 60 and 70. The usual site is at the bifurcation in the common duct. Cancer at the distal end of the common duct is commonly confused with cancer of the pancreas. Characteristically, metastatic spread occurs to local lymph nodes, the liver, lungs, and the peritoneum.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Gastric cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The cause of gastric cancer is unknown. It's commonly associated with gastritis with gastric atrophy, which may result from gastric cancer and may not be a precursor state. Predisposing factors include environmental influences, such as smoking and high alcohol intake. Genetic factors have also been implicated because this disease occurs more commonly among people with type A blood than among those with type O; similarly, it's more common in people with a family history of gastric cancer. Dietary factors also seem related, including types of food preparation, physical properties of some foods, and certain methods of food preservation (especially smoking, pickling, or salting). There's a strong correlation between infection with Helicobacter pylori and distal gastric cancer.
Gastric cancer is common throughout the world and affects all races; however, unexplained geographic and cultural differences in incidence occur — for example, a higher mortality in Japan, Iceland, Chile, and Austria. In the United States, during the past 25 years, incidence has decreased by 50% and the resulting death rate is one-third what it was 30 years ago. Incidence is higher in males older than 40. Hispanic, Native, and African Americans are twice as likely to develop gastric cancer than Whites. The prognosis depends on the stage of the disease at the time of diagnosis; however, the overall 5-year survival rate is approximately 19%.
The decrease in gastric cancer in the United States has been attributed, without proof, to the balanced American diet and to refrigeration, which reduces nitrate-producing bacteria in food.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Kidney cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The causes of kidney cancer aren't known, although smokers develop more renal cell tumors than nonsmokers. However, the incidence of this malignancy is rising, possibly as a result of exposure to environmental carcinogens as well as increased longevity. Even so, this cancer accounts for only about 2% of all adult cancers. Kidney cancer is more common in men than women and peaks in incidence between ages 50 and 70.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Laryngeal cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
In laryngeal cancer, major predisposing factors include smoking and alcoholism; minor factors include chronic inhalation of noxious fumes and familial tendency. Cancer of the larynx rarely occurs in nonsmokers.
Laryngeal cancer is classified according to its location:
❑supraglottis (false vocal cords)
❑glottis (true vocal cords)
❑subglottis (downward extension from vocal cords [rare]).
The ratio of male to female incidence is 3.8:1. Most victims are between ages 50 and 65.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Liver cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
The immediate cause of liver cancer is unknown, but it may be a congenital disease in children. Adult liver cancer may result from environmental exposure to carcinogens, such as the chemical compound aflatoxin (a mold that grows on rice and peanuts), thorium dioxide (a contrast medium formerly used in liver radiography), Senecio alkaloids, and possibly androgens and oral estrogens.
Roughly 30% to 70% of patients with hepatomas also have cirrhosis. (Hepatomas are 40 times more likely to develop in a cirrhotic liver than in a normal one.)
Whether cirrhosis is a premalignant state or alcohol and malnutrition predispose the liver to develop hepatomas is still unclear. Other risk factors are exposure to the hepatitis C virus and the hepatitis B virus.
Liver cancer accounts for roughly 1% of all cancers in the United States and for 10% to 50% in Africa and parts of Asia. Liver cancer is most prevalent in men (particularly men older than age 60), and incidence increases with age. It's rapidly fatal, usually within 6 months, from GI hemorrhage, progressive cachexia, hepatic failure, or metastasis.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Lung cancer:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
Most experts agree that lung cancer is attributable to inhalation of carcinogenic pollutants by a susceptible host. Who's most susceptible? Any smoker older than age 40, especially if he began to smoke before age 15, has smoked a whole pack or more per day for 20 years, or works with or near asbestos.
Pollutants in tobacco smoke cause progressive lung cell degeneration. Lung cancer is 10 times more common in smokers than in nonsmokers; 80% of patients with lung cancer are smokers. Cancer risk is determined by the number of cigarettes smoked daily, the depth of inhalation, how early in life smoking began, and the nicotine content of cigarettes. Two other factors also increase susceptibility: exposure to carcinogenic industrial and air pollutants (asbestos, uranium, arsenic, nickel, iron oxides, chromium, radioactive dust, and coal dust) and familial susceptibility.
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Breast cancer:
Causes
(Handbook of Diseases)
The cause of breast cancer is unknown, but its high incidence in women implicates estrogen. Certain predisposing factors are clear; women at high risk include those who:
❑ have a family history of breast cancer
❑ have long menses; began menses early or menopause late
❑ have never been pregnant
❑ were first pregnant after age 31
❑ have had unilateral breast cancer
❑ have had endometrial or ovarian cancer
❑ have been exposed to low-level ionizing radiation.
Many other predisposing factors have been investigated, including estrogen therapy, antihypertensives, high-fat diet, obesity, and fibrocystic disease of the breasts.
Women at lower risk include those who:
❑ were pregnant before age 20
❑ have had multiple pregnancies
❑ are Indian or Asian.
Pathophysiology
Breast cancer is more common in the left breast than in the right and more common in the upper outer quadrant. Growth rates vary. Theoretically, slow-growing breast cancer may take up to 8 years to become palpable at 1 cm in size. It spreads by way of the lymphatic system and the bloodstream, through the right side of the heart to the lungs and, eventually, to the other breast, the chest wall, liver, bone, and brain.
Many refer to the estimated growth rate of breast cancer as doubling time, or the time it takes the malignant cells to double in number. Survival time for breast cancer is based on tumor size and spread; the number of involved nodes is the single most important factor in predicting survival time.
Classified by histologic appearance and location of the lesion, breast cancer may be:
❑ adenocarcinoma — arising from the epithelium
❑ intraductal — developing within the ducts (includes Paget’s disease)
❑ infiltrating — occurring in parenchymatous tissue of the breast
❑ inflammatory (rare) — reflecting rapid tumor growth, in which the overlying skin becomes edematous, inflamed, and indurated
❑ lobular carcinoma in situ — reflecting tumor growth involving lobes of glandular tissue
❑ medullary or circumscribed — a large tumor with a rapid growth rate.
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Source: Handbook of Diseases, 2003
Spinal neoplasms:
Causes
(Handbook of Diseases)
Primary spinal cord tumors may be extramedullary (occurring outside the spinal cord) or intramedullary (occurring within the cord itself). Extra-medullary tumors may be intradural (meningiomas and schwannomas), which account for 60% of all primary spinal cord neoplasms, or extradural (metastatic tumors from breasts, lungs, prostate, leukemia, or lymphomas), which account for 25% of these neoplasms.
Intramedullary tumors, or gliomas (astrocytomas or ependymomas), are comparatively rare, accounting for only about 10% of tumors. In children, they’re low-grade astrocytomas.
Spinal cord tumors are rare compared with intracranial tumors (ratio of 1:4). They occur with equal frequency in men and women, with the exception of meningiomas, which occur most often in women. Spinal cord tumors can occur anywhere along the length of the cord or its roots.
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Source: Handbook of Diseases, 2003
Bladder cancer:
Causes
(Handbook of Diseases)
Certain environmental carcinogens — such as 2-naphthylamine, benzidine, tobacco, and nitrates — predispose people to transitional cell tumors. Thus, workers in certain industries (rubber workers, weavers, leather finishers, aniline dye workers, hairdressers, petroleum workers, and spray painters) are at high risk for such tumors. The period between exposure to the carcinogen and development of symptoms is about 18 years.
Squamous cell carcinoma of the bladder is most common in geographic areas where schistosomiasis is endemic. It’s also associated with chronic bladder irritation and infection (for example, from kidney stones, indwelling urinary catheters, and cystitis caused by cyclophosphamide).
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Source: Handbook of Diseases, 2003
Cervical cancer:
Causes
(Handbook of Diseases)
The human papillomavirus (HPV) is accepted as the cause of virtually all cervical dysplasias and cervical cancers. Certain strains of the HPV (16, 18, 31) are associated with an increased risk of cervical cancer. Several predisposing factors have been related to the development of cervical cancer: intercourse at a young age (younger than age 16), multiple sexual partners, and herpesvirus 2 and other bacterial or viral venereal infections.
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Source: Handbook of Diseases, 2003
Colorectal cancer:
Causes
(Handbook of Diseases)
The exact cause of colorectal cancer is unknown, but studies showing concentration in areas of higher economic development suggest a relation to diet (excess animal fat, particularly beef, and low fiber). Other factors that increase the risk of developing colorectal cancer include:
❑ other diseases of the digestive tract
❑ age (older than 40)
❑ history of ulcerative colitis (the average interval before onset of cancer is 11 to 17 years)
❑ familial polyposis (cancer almost always develops by age 50).
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Source: Handbook of Diseases, 2003
Esophageal cancer:
Causes
(Handbook of Diseases)
The cause of esophageal cancer is unknown, but predisposing factors include chronic irritation caused by heavy smoking and excessive use of alcohol, stasis-induced inflammation, and nutritional deficiency. Esophageal tumors are usually fungating and infiltrating. Most arise in squamous cell epithelium, a few are adenocarcinomas, and fewer still are melanomas and sarcomas.
Esophageal cancer has a 5-year survival rate below 10%, and regional metastasis occurs early by way of submucosal lymphatics. Metastasis produces such serious complications as tracheoesophageal fistulas, mediastinitis, and aortic perforation. Common sites of distant metastasis include the liver and lungs.
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Source: Handbook of Diseases, 2003
Gallbladder and bile duct cancers:
Causes
(Handbook of Diseases)
Many consider gallbladder cancer a complication of gallstones. This inference rests on circumstantial evidence from postmortem examinations: 60% to 90% of all gallbladder cancer patients also have gallstones. Postmortem data from patients with gallstones show gallbladder cancer in only 0.5%.
Adenocarcinoma accounts for 85% to 95% of all cases of gallbladder cancer; squamous cell carcinoma accounts for 5% to 15%. Mixed-tissue types are rare.
Lymph node metastasis is present in 25% to 70% of patients at diagnosis. Direct extension to the liver is common (46% to 89% of patients); direct extension to the cystic and the common bile ducts as well as the stomach, colon, duodenum, and jejunum produces obstructions. Metastasis also occurs through the portal or hepatic veins to the peritoneum, ovaries, and lower lung lobes.
The cause of extrahepatic bile duct cancer isn’t known, but statistics reveal an unexplained increased incidence of this cancer in patients with ulcerative colitis. This association may be attributed to a common cause — perhaps an immune mechanism or chronic use of certain drugs by the patient with colitis.
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Source: Handbook of Diseases, 2003
Gastric cancer:
Causes
(Handbook of Diseases)
The cause of gastric cancer is unknown. This cancer is commonly associated with gastritis, chronic inflammation of the stomach, gastric ulcers, Helicobacter pylori bacteria, and gastric atrophy. Predisposing factors include environmental influences, such as smoking and high alcohol intake.
Genetic factors have also been implicated because this disease occurs more frequently among people with type A blood than among those with type O; similarly, it’s more common in people with a family history of such cancer.
Dietary factors include types of food preparation, physical properties of some foods, and certain methods of food preservation (especially smoking, pickling, and salting).
Classification
According to gross appearance, gastric cancer can be classified as polypoid, ulcerating, ulcerating and infiltrating, or diffuse. The parts of the stomach affected by gastric cancer, listed in order of decreasing frequency, are the pylorus and antrum (50%), the lesser curvature (25%), the cardia (10%), the body of the stomach (10%), and the greater curvature (2% to 3%).
Metastasis
Gastric cancer metastasizes rapidly to the regional lymph nodes, omentum, liver, and lungs by the following routes: walls of the stomach, duodenum, and esophagus; lymphatic system; adjacent organs; bloodstream; and peritoneal cavity.
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Source: Handbook of Diseases, 2003
Kidney cancer:
Causes
(Handbook of Diseases)
The cause of kidney cancer is unknown. However, the incidence of this cancer is rising, possibly as a result of exposure to environmental carcinogens as well as increased longevity. Even so, kidney cancer accounts for only about 2% of all adult cancers. It’s twice as common in men as in women and usually affects patients older than age 40.
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Source: Handbook of Diseases, 2003
Laryngeal cancer:
Causes
(Handbook of Diseases)
With laryngeal cancer, major predisposing factors include smoking and alcoholism; minor factors include chronic inhalation of noxious fumes and familial tendency.
Laryngeal cancer is classified according to its location:
❑ supraglottis (false vocal cords)
❑ glottis (true vocal cords)
❑ subglottis (downward extension from the vocal cords [rare]).
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Source: Handbook of Diseases, 2003
Liver cancer:
Causes
(Handbook of Diseases)
The immediate cause of liver cancer is unknown, but it may be a congenital disease in children. Adult liver cancer may result from environmental exposure to carcinogens, such as the chemical compound aflatoxin (a mold that grows on rice and peanuts), thorium dioxide (a contrast medium formerly used in liver radiography), Senecio alkaloids, androgens, or oral estrogens.
Risk factors
Roughly 30% to 70% of patients with hepatomas also have cirrhosis. (Hepatomas are 40 times more likely to develop in a cirrhotic liver than in a normal one.) Whether cirrhosis is a premalignant state or alcohol and malnutrition predispose the liver to develop hepatomas is still unclear. Another risk factor is exposure to the hepatitis B virus, although this risk will probably decrease with the availability of the hepatitis B vaccine.
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Source: Handbook of Diseases, 2003
Lung cancer:
Causes
(Handbook of Diseases)
Most experts agree that lung cancer is attributable to inhalation of carcinogenic pollutants by a susceptible host. Most susceptible are those persons who smoke or who work with or near asbestos.
Pollutants in tobacco smoke cause progressive lung cell degeneration. Lung cancer is 10 times more common in smokers than in nonsmokers; indeed, 80% of lung cancer patients are or were smokers.
Cancer risk is determined by the number of cigarettes smoked daily, the depth of inhalation, how early in life smoking began, and the nicotine content of the cigarettes. Two other factors also increase susceptibility: exposure to carcinogenic industrial and air pollutants (asbestos, uranium, arsenic, nickel, iron oxides, chromium, radioactive dust, and coal dust), and familial susceptibility.
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Source: Handbook of Diseases, 2003
Ovarian cancer:
Causes
(Handbook of Diseases)
The exact cause of ovarian cancer is unknown, but its incidence is noticeably higher in women of upper socioeconomic levels between the ages of 20 and 54. However, it can occur during childhood. Certain genes, including BRCA1 and BRCA2, may increase risk. Other contributing factors include age at menopause; infertility; celibacy; high-fat diet; exposure to asbestos, talc, and industrial pollutants; nulliparity; familial tendency; and history of breast or uterine cancer.
Primary epithelial tumors arise in the müllerian epithelium; germ cell tumors, in the ovum itself; and sex cord tumors, in the ovarian stroma (the ovary’s supporting framework).
Ovarian tumors spread rapidly intraperitoneally by local extension or surface seeding and, occasionally, through the lymphatics and the bloodstream. Generally, extraperitoneal spread is through the diaphragm into the chest cavity, which may cause pleural effusions. Other types of metastasis are rare.
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Source: Handbook of Diseases, 2003
Pancreatic cancer:
Causes
(Handbook of Diseases)
Pancreatic cancer, the fourth leading cause of cancer-related death in the United States, is slightly more common in men than in women; risk increases with age. Almost one-third of cases result from cigarette smoking; some cases are related to hereditary syndromes.
Possible predisposing factors are chronic pancreatitis, diabetes mellitus, and chronic alcohol abuse.
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Source: Handbook of Diseases, 2003
Prostatic cancer:
Causes
(Handbook of Diseases)
Although androgens regulate prostate growth and function and may also speed tumor growth, no definite link between increased androgen levels and prostatic cancer has been found. When primary prostatic lesions metastasize, they typically invade the prostatic capsule and spread along the ejaculatory ducts in the space between the seminal vesicles or perivesicular fascia.
Prostatic cancer accounts for about 18% of all cancers. The incidence is highest in Blacks and lowest in Asians. Incidence also increases with age more rapidly than any other cancer.
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Source: Handbook of Diseases, 2003
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