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CANCER • Cancer is a term used to describe a large group of diseases that are characterized by a cellular malfunction. Healthy cells are programmed to “know what to do and when to do it”. Cancerous cells do not have this programming and therefore grow and replicate out of control. They also serve no physiological function. These cells are now termed a neoplasm.
CANCER • A disease caused by uncontrolled cell growth. • Tumors are a mass of uncontrolled growing cells that form a clump. • Malignant- invade and destroys healthy tissue • Benign- harmless cell mass
Metastasis Metastasis is a complex process that involves the spread of a tumor or cancer to distant parts of the body from its original site. However, this is a difficult process. Illustration showing hematogeneous metastasis
Different Types of Cells • Blood cells • Muscle cells (smooth, striated, cardiac) • Nerve cells • Bone cells • Cartilage cells • Liver (hepa) cells
Classification • Cancers are classified by the type of cell. These types include: • Carcinoma: Cancers derived from epithelial cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the breast, lung, pancreas, and colon. • Sarcoma: Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve).
Lymphoma and leukemia: These two classes of cancer arise from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. • Germ cell tumor: Cancers derived from pluripotent cells, most often presenting in the testicle or the ovary • Blastoma: Cancers derived from immature "precursor" cells or embryonic tissue. These are also most common in children.
Types of Cancer • Breast • Respiratory • Colon • Urinary • Skin • Leukemia • Ovarian • Cervical
Signs and symptoms • Cancer symptoms can be divided into three groups: • Local symptoms: are restricted to the site of the primary cancer. They can include lumps or swelling (tumor), hemorrhage (bleeding from the skin, mouth or anus), ulceration and pain. Although local pain commonly occurs in advanced cancer, the initial swelling is often painless.
Metastatic symptoms: are due to the spread of cancer to other locations in the body. They can include enlarged lymph nodes (which can be felt or sometimes seen under the skin), hepatomegaly (enlarged liver) or splenomegaly (enlarged spleen) which can be felt in the abdomen, pain or fracture of affected bones, and neurological symptoms. • Systemic symptoms: occur due to distant effects of the cancer that are not related to direct or metastatic spread. Some of these effects can include weight loss, fatigue, excessive sweating, anemia (low red blood cell count).
Causes It is almost always impossible to prove exactly what caused a cancer in any individual, because most cancers have multiple possible causes. Cancers are primarily an environmental disease with 90-95% of cases attributed to environmental factors and 5-10% due to genetics. Common environmental factors that contribute to cancer death include tobacco (25-30%), diet and obesity (30-35%), infections (15-20%), radiation (both ionizing and non-ionizing, up to 10%), stress, lack of physical activity, and environmental pollutants.
Chemicals The incidence of lung cancer is highly correlated with smoking. Cancer pathogenesis is traceable back to DNA mutations that impact cell growth and metastasis. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with many forms of cancer, and causes 90% of lung cancer. Tobacco smoke contains over fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons.
Millions of workers run the risk of developing cancers such as lung cancer from inhaling asbestos fibers and tobacco smoke, or leukemia from exposure to benzene at their workplaces. Diet and exercise Diet, physical inactivity, and obesity are related to approximately 30–35% of cancer cases. Diets that are low in vegetables, fruits and whole grains, and high in processed or red meats are linked with a number of cancers. A high salt diet is linked to gastric cancer, aflatoxin B1, a frequent food contaminate, with liver cancer, and Betel nut chewing with oral cancer.
Infection Worldwide approximately 18% of cancers are related to infectious diseases. Viruses are usual infectious agents that cause cancer. A virus that can cause cancer is called an oncovirus. These include human papillomavirus (cervical carcinoma), Epstein-Barr virus (B-cell lymphoproliferative disease), hepatitis B and hepatitis C viruses (hepatocellular carcinoma), and Human T-cell leukemia virus-1 (T-cell leukemias). Bacterial infection include Helicobacter pylori-induced gastric carcinoma.
Radiation Up to 10% of invasive cancers are related to radiation exposure, including both ionizing radiation and non-ionizing radiation. Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies which are the most common forms of cancer in the world. Non-ionizing radio frequency radiation from mobile phones, electric power transmission, and other similar sources have been described as a possible carcinogen by the World Health Organization's International Agency for Research on Cancer.
Heredity • The vast majority of cancers are non-hereditary, which are called sporadic cancers. Hereditary cancers are cancers that are primarily caused by an inherited genetic defect (less than 0.3% of the population are carriers of a genetic mutation). They cause less than 3–10% of all cancer. Some of these syndromes include: • certain inherited mutations in the genes BRCA1 and BRCA2 with a more than 75% risk of breast cancer and ovarian cancer
Diagnosis Most cancers are initially recognized through cancer screening. which usually requires the opinion of a pathologist, a type of physician (medical doctor) who specializes in the diagnosis of cancer and other diseases. People with suspected cancer are investigated with medical tests. These commonly include blood tests, X-rays, CT scans and endoscopy.
Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, other tests, or medical imaging. Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. E.g., screening mammography once for every two years for all women aged 50–74. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Detecting • Self-exam • Biopsy • X rays • MRI • Blood and DNA tests
Computed tomography (CT scanning) is a medical imaging modality where tomographic images or slices of specific areas of the body are obtained from a large series of two-dimensional X-ray images taken in different directions. These cross-sectional images can be combined into a three-dimensional image of the inside of the body and used for diagnostic and therapeutic purposes in various medical disciplines.
TREATMENT • Surgery-remove tissue • Chemotherapy-use of drugs (The first modern chemotherapeutic agent was arsphenamine an arsenic compound, most chemotherapeutic drugs work by impairing mitosis (cell division), effectively targeting fast-dividing cells) • Radiation therapy-beam of radiation to fire at a tumor • Combination- use any or all treatments
Preventing Cancer • Don’t’ smoke! • Wear sunscreen; • Eat your veggies and cut the fat • Stay active • Get regular medical check-ups
