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Gordon, Dr. Jerry. "How Cancer Works." 01 April 2000. HowStuffWorks.com. <http://health.howstuffworks.com/cancer.htm> 09 May 2008.
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Causes of Cancer
Cancer is caused by a number of factors, some of which we can control, and some we cannot. One of the uncontrollable factors is the presence of gene mutations. One type of gene that plays a role in normal cell growth -- an oncogene -- can be altered to contribute to the uncontrolled growth of a tumor. Oncogenes affect the way cells use energy and multiply. For example, in some cancers, the ras gene (an oncogene) is mutated, and produces a protein that stimulates cells to divide prematurely. Other oncogenes, such as C-myc and C-erb B-2, when amplified, are implicated in small cell lung cancer and breast cancer, respectively.Mutations in tumor suppressor genes are another common cause of cancer. As you might expect, a tumor suppressor gene is supposed to prevent tumors. But when these genes are damaged, they can allow cancer to develop instead of preventing it. One of these genes, p53, normally prevents cells with abnormal DNA from surviving. When p53 is defective, these cells with abnormal DNA survive and can multiply, increasing the probability of developing cancer.
Certain cancers are associated with chromosomal abnormalities. Chromosomes are located within the nucleus of our cells, and contain our genes. When genes are missing, duplicated, or rearranged, a predisposition to develop a tumor is increased. Certain leukemias, sarcomas, lymphomas, and others tumors are associated with chromosomal abnormalities.
There are also viruses associated with cancer. The human papillomavirus (HPV) that causes genital warts is associated with carcinoma of the cervix, and the Epstein-Barr virus that causes infectious mononucleosis, is associated with Burkitt's lymphoma. Diseases or drugs that affect the immune system can also increase the risk for certain cancers. The disease AIDS, for instance, is associated with a high risk of two types of cancer, namely, Kaposi's sarcoma and lymphoma.
Exposure to ionizing radiation can increase the risk of certain cancers. X-rays used to treat disorders such as acne or adenoid enlargement can increase the risk of certain types of leukemias and lymphomas.
Fortunately, there are also factors under our control that can increase the risk of getting cancer, and can therefore be avoided. There are substances called carcinogens (cancer-forming agents) that can increase the risk of getting cancer. Some common carcinogens include:
- Arsenic, asbestos, and nickel, which can cause lung and other cancers
- Benzene, which can cause leukemia
- Formaldehyde, which can cause nasal and nasopharyngeal cancer
- and many others...
Unprotected exposure to sunlight (ultraviolet radiation) is associated with skin cancer. The main cancers caused by sunlight are basal cell carcinoma, squamous cell carcinoma and malignant melanoma.
We'll define some terminology that doctors use when they talk about cancer in the next section.
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SYMPTOM CHECKER:
Abdominal Bloating Abdominal Fullness Prematurely Afte... Abdominal Lumps Abdominal Mass Abdominal Pain Abdominal Rigidity Abdominal Sounds Abdominal Swelling Abnormal Posturing Abnormal Tooth Shape Abnormally Dark Or Light Skin Absent Menstruation Absent Thirst Agitation Ambiguous Genitalia Ankle Pain Appetite Decrease Appetite Increase Apraxia Arachnodactyly Armpit Lump Autistic Behavior Babinski's Reflex Bed Wetting Belching Binge Eating Blackheads Bleeding Gums Bleeding Into The Skin Blindness Blockage Of Leg Arteries Blood In The Semen Blood in Urine Bloody Or Tarry Stools Bone Pain Or Tenderness Bounding Pulse Bowel Incontinence Breast Lump Breast Pain Breath Odor Breath Sounds Breathing - Slowed Or Stopped Breathing Difficulty Breathing Difficulty When Lying Dow... Breathing That Sounds Abnormal Broad Nasal Bridge Bulging Fontanelles Bullae Chemosis Chest Pain Chills Clammy Skin Claw Foot Claw Hand Cloudy Cornea Clubbing Of The Fingers Or Toes Cold Intolerance Coloboma Of The Iris Comedones Confusion Constipation Contracture Deformity Coughing Coughing Up Blood Crying Excessively in Infants Cyst Decerebrate Posture Decorticate Posture Decreased Consciousness Decreased Urine Output Delayed Growth Delayed or Absent Tooth Formation Depression Diarrhea Difficulty with Urination Dizziness Drooling Drowsiness Dry Eyes Dry Hair Dry Skin Ear Discharge Earache Earlobe Creases Elbow Pain Epicanthal Folds Erection Problems Erosion Excessive Or Unwanted Hair In Women Excessive Thirst Excessive Urination Excessive Urination at Night Excessively Large Fontanelles Eye Burning, Itching and Discharge Eye Pain Eye Redness Eye Slant Eyelid Drooping Eyes That Bulge Face Pain Facial Paralysis Facial Swelling Fainting Fatigue Female Sexual Dysfunction Fever Finger Pain Fingers That Change Color Flank Pain Floating Stools Focal Neurological Deficits Foot Pain Foot, Leg, And Ankle Swelling Foul Smelling Stools Frequent Or Urgent Urination Frontal Bossing Gas (Flatulence) Gastrointestinal Bleeding Genital Sores (Female) Genital Sores (Male) Groin Lumps Groin Pain Gynecomastia Hair Loss Hallucinations Hand Or Foot Spasms Hand Tremors Headache Hearing Loss Heart Murmurs And Other Sounds Heart Palpitations Heartburn Heat Intolerance Heavy, Prolonged, or Irregular Mens... Heel Pain Hemolytic Crisis Hepatomegaly Heterochromia Hiccups Hip Pain Hoarseness Or Changing Voice Hump Behind The Shoulders Hyperactivity Hyperelastic Skin Hypermobile Joints Hyperventilation Hypotonia Impaired Smell Increased Head Circumference Indigestion Infantile Reflexes Intercostal Retractions Intertrigo Irritability Itching Jaundice (Yellow Skin) Joint Pain Joint Swelling Knee Pain Leg Pain Lichenified Limited Range Of Motion Lordosis Low Nasal Bridge Lower Back Pain Macule Malaise Memory Loss Metopic Ridge Microcephaly Micrognathia Morbid Obesity Morning Sickness Moro Reflex Motormental Retardation Mouth Sores Muscle Aches Muscle Atrophy Muscle Cramps Muscle Function Loss Muscle Twitching Nail Abnormalities Nasal Congestion Nasal Discharge Nasal Flaring Natal Teeth Nausea And Vomiting Neck Lumps Neck Pain Night Blindness Nightmares Nikolsky’s Sign Nipple Discharge Nodules Nosebleed Numbness And Tingling Obesity Opisthotonos Pain During Sexual Intercourse Painful Menstrual Periods Painful Urination Pale or Clay-Colored Stools Paleness Papule Patches Patchy Skin Color Pectus Carinatum Pectus Excavatum Penis Pain Photophobia Pilonidal Dimple Pinna Abnormalities And Low-set Ear... Point Tenderness Polydactyly Polyhydramnios Poor Feeding In Infants Preauricular Tag Or Pit Premenstrual Breast Tenderness and ... Prognathism Pupils That Are Different Sizes Purpura Pustules Rapid Shallow Breathing Rash in a Child Under 2 Years Rashes Rib Cage Pain Ridged Sutures Scales Scrotal Swelling Seizures Sensorineural Deafness Separated Sutures Shin Splints Short Philtrum Short Stature Shoulder Pain Simian Crease Skeletal Limb Abnormalities Skin Blushing/flushing Skin Discoloration Skin Lumps Skin Turgor Sleeping Difficulty Sneezing Snoring Sore Throat Spasticity Speech Impairment (adult) Splenomegaly Splinter Hemorrhages Strange Behavior Stress And Anxiety Striae Subcutaneous Emphysema Sunburn Sunken Fontanelles Supernumerary Nipples Swallowing Difficulty Swallowing Pain Or Burning Sweating Sweating Decrease Swelling Swollen Glands Swollen Gums Taste Impairment Telangiectasia Tenesmus Testicle Lump Testicle Pain Tinnitus Tongue Problems Tooth Discoloration Toothaches Ulcers Uncontrollable Eye Movements Uncontrollable Movement Uncontrolled Or Slow Movement Uncoordinated Movement Unpredictable Or Jerky Movement Urinary Incontinence Urine Discoloration Vaginal Bleeding Between Periods Vaginal Bleeding In Pregnancy Vaginal Discharge Vaginal Itching Vesicles Vision Problems Vomiting Blood Walking Abnormalities Watery Eyes Weak or Absent Pulse Weakness Webbing Of The Fingers Or Toes Weight Gain Weight Loss Wheezing White Spots in the Pupil Whitehead Widely Spaced Teeth Wrinkles Wrist Pain Yawning
DISEASES AND CONDITIONS GLOSSARY:
Aarskog Syndrome Aase Syndrome Abdominal Aortic Aneurysm ABO Incompatibility Abortion - Complete Abortion - Elective Or Therapeutic Abortion - Incomplete Abortion - Infected Abortion - Threatened Abscess Acanthosis Nigricans Achalasia Achilles Tendinitis Achondrogenesis Achondroplasia Acidosis Acne Acoustic Neuroma Acoustic Trauma Acquired Platelet Function Defect Acrodermatitis Acrodysostosis Acromegaly Actinic Keratosis Actinomycosis Acute Adrenal Crisis Acute Arterial Occlusion - Kidney Acute Bilateral Obstructive Uropath... Acute Bronchitis Acute Cerebellar Ataxia Acute Cholecystitis (Gallstones) Acute Cytomegalovirus (CMV) Infecti... Acute Gouty Arthritis Acute HIV Infection Acute Interstitial Nephritis Not NS... Acute Kidney Failure Acute Lymphocytic Leukemia (ALL) Acute Mountain Sickness Acute Myeloid Leukemia Acute Nephritic Syndrome Acute Pancreatitis Acute Tubular Necrosis Acute Unilateral Obstructive Uropat... Acute Upper Airway Obstruction Addison’s Disease Adenomyosis Adhesion Adjustment Disorder Adolescent Depression Adolescent Pregnancy Adrenocortical Carcinoma Adrenoleukodystrophy Adult Still's Disease Agammaglobulinemia Age-related Hearing Loss Agoraphobia Agranulocytosis Aicardi Syndrome AIDS Albinism Alcohol Withdrawal Alcoholic Cardiomyopathy Alcoholic Ketoacidosis Alcoholic Liver Disease Alcoholic Neuropathy Alcoholism Alkalosis Alkaptonuria Allergic Conjunctivitis Allergic Rhinitis Allergic Vasculitis Allergies Allergy To Mold - Dander - Dust Alopecia Areata Alpha-1 Antitrypsin Deficiency Alport Syndrome Alström Syndrome Alveolar Abnormalities Alzheimer’s Disease Amaurosis Fugax Amblyopia Amebiasis Amebic Liver Abscess Amelogenesis Imperfecta Amenorrhea Amniotic Constriction Bands Amphetamine Or Sympathomimetic Into... Amyotrophic Lateral Sclerosis Anal Fissure Analgesic Nephropathy Anaphylaxis Anaplastic Thyroid Cancer Androgen Insensitivity Syndrome Anemia Anemia - B12 Deficiency Anemia Of Chronic Disease Anencephaly Aneurysm Aneurysm In The Brain Angina Angiodysplasia Of The Colon Angioedema Ankylosing Spondylitis Annular Pancreas Anorchia Anorectal Abscess Anorexia Nervosa Anthrax Antisocial Personality Disorder Aortic Arch Syndrome Aortic Dissection Aortic Insufficiency Aortic Stenosis Apert Syndrome Apnea Of Prematurity Apoplexy Appendicitis ARDS (acute Respiratory Distress Sy... Arrhenoblastoma of the Ovary Arrhythmias Arterial Embolism Arterial Insufficiency Arteriosclerosis Of The Extremities Arteriovenous Malformation - Cerebr... Arthritis Asbestos-related Pleural Effusion Asbestosis Ascariasis Ascites Aseptic Meningitis Aseptic Necrosis Asherman Syndrome Asperger Syndrome Aspergillosis Aspiration Pneumonia Asthma Astigmatism Asymptomatic Bacteriuria Asymptomatic HIV Infection Ataxia-telangiectasia Atelectasis Atheroembolic Renal Disease Atherosclerosis Athlete's Foot Atrial Fibrillation/flutter Atrial Myxoma Atrial Septal Defect Atrophic Vaginitis Attention Deficit Hyperactivity Dis... Atypical Mycobacterial Infection Atypical Pneumonia Aural Polyps Autism Autoerythrocyte Sensitivity Autoimmune Disorders Autoimmune Hepatitis Autonomic Hyperreflexia Autonomic Neuropathy Avian Influenza Avoidant Personality Disorder Axillary Nerve Dysfunction Bacterial Gastroenteritis Baker’s Cyst Balanitis Barbiturate Intoxication And Overdo... Barrett’s Esophagus Bartholin’s Abscess Bartter Syndrome Basal Cell Carcinoma Basal Cell Nevus Syndrome Basal Ganglia Dysfunction Bassen-Kornzweig Syndrome Bathing Trunk Nevus Becker's Muscular Dystrophy Beckwith-Wiedemann Syndrome Bedwetting Bell's Palsy Benign Ear Cyst Or Tumor Benign Positional Vertigo Beriberi Bezoar Bilateral Hydronephrosis Bile Duct Obstruction Biliary Atresia Biliary Stricture Bipolar Disorder Birth-acquired Herpes Birthmarks - Pigmented Birthmarks - Red Bladder Cancer Bladder Outlet Obstruction Bladder Stones Blastomycosis Blastomycosis Skin Lesion Bleeding Disorders Bleeding Esophageal Varices Blepharitis Blind Loop Syndrome Blocked Tear Duct Blood Clots Blount's Disease Body Lice Bone Tumors Borderline Personality Disorder Botulism Bowlegs Brachial Palsy In Newborns Brachial Plexopathy Brain Abscess Brain Herniation Brain Tumor - Adults Brain Tumor - Children Branchial Cleft Cyst Breast Cancer Breast Infection Breast Milk Jaundice Breath Holding Spell Brief Reactive Psychosis Bronchial Adenoma Bronchiectasis Bronchiolitis Bronchitis Bronchopulmonary Dysplasia Brucellosis Bruxism Bulimia Bullous Pemphigoid Bunions Burkitt Lymphoma Bursitis Byssinosis Campylobacter Enteritis Canavan Disease Cancer Cancer - Penis Cancer - Renal Pelvis Or Ureter Cancer - Throat Or Larynx Cancer - Vulva Candida Esophagitis Canker Sores Caplan Syndrome Caput Succedaneum Carbunculosis Carcinoid Syndrome Cardiac Amyloidosis Cardiac Tamponade Cardiogenic Shock Cardiomyopathy Carpal Tunnel Syndrome