Because Cancer begins at the microscopic cellular level, the first signs of a malignant (actively cancerous) growth are nearly impossible to detect without special tests and training. In the case of pancreatic cancer, for example, there is little to no pain involved as the first malignant cells form around the organ. As the tumor becomes more organized, new blood vessels may form to feed it directly or older vessels may be diverted. Meanwhile, the host body may only experience a few symptoms which resemble many other conditions besides cancer. Only after a sample of suspicious tissue has been removed and tested (biopsied) can many cancer forms be diagnosed.
One of the most insidious aspects of Cancer is the way it grows. As the tumor outgrows the original organ, pieces of malignant tissue often break off (metastasize)and enter the bloodstream or lymph system. The cancer cells can then attach themselves to other vulnerable organs and form new tumors. Thus a patient with pancreatic cancer may eventually suffer from lung, brain, kidney, breast or colon cancer as well. This is why cancer specialists (oncologists) place so much emphasis on containing malignant tumors to their place of origin.
One of the most insidious aspects of Cancer is the way it grows. As the tumor outgrows the original organ, pieces of malignant tissue often break off (metastasize)and enter the bloodstream or lymph system. The cancer cells can then attach themselves to other vulnerable organs and form new tumors. Thus a patient with pancreatic cancer may eventually suffer from lung, brain, kidney, breast or colon cancer as well. This is why cancer specialists (oncologists) place so much emphasis on containing malignant tumors to their place of origin.
Treatment for Cancer ranges from rounds of powerful chemicals to focused burst of radiation to complete surgical removal of the tumor and surrounding tissue. Each treatment type brings a certain level of risk and pain to the patient, but cancerous cells left untreated will almost inevitably choke off vital organs and circulation. Chemotherapy introduces strong medicines which target fast-growing cells, but this also includes normal events such as hair growth and digestion. Radiation treatments use heat energy to literally burn off malignant cells, but healthy tissue is also damaged. Surgical removal can lead to a permanent recovery, but undetected malignant cells may have already metastasized to other organs or be jarred loose by the surgery itself.
Curing Cancer has been a major goal of medical researchers for decades, but development of new treatments takes time and money. Already there are many forms of cancer which are no longer considered untreatable. Some cancers, such as leukemia (blood cancer), can actually stop growing as suddenly as they started. This is called remission, and is often seen as a tremendous blessing for patients who have fought their conditions for years. Science may yet find the root causes of all cancers and develop safer methods for shutting them down before they have a chance to grow or spread.
Curing Cancer has been a major goal of medical researchers for decades, but development of new treatments takes time and money. Already there are many forms of cancer which are no longer considered untreatable. Some cancers, such as leukemia (blood cancer), can actually stop growing as suddenly as they started. This is called remission, and is often seen as a tremendous blessing for patients who have fought their conditions for years. Science may yet find the root causes of all cancers and develop safer methods for shutting them down before they have a chance to grow or spread.
HOW CANCER DEVELOPS
A healthy human body is composed of 30 trillion cells, most of which are in constant turnover as cells die and others reproduce to replace them in an orderly fashion. Healthy cells of the skin, hair, lining of the stomach, and blood, for example, regularly reproduce by dividing to form two daughter cells (see Mitosis). This cell division cycle proceeds under the regulation of the body’s intricately tuned control system. Among other functions, this control system ensures that cells only divide when needed, so that organs and tissues maintain their correct shape and size. Should this system fail, a variety of backup safety mechanisms prevent the cell from dividing uncontrollably. In order for a cell to become cancerous, every one of these safety mechanisms must fail.
Cancer begins in genes, bits of biochemical instructions composed of individual segments of the long, coiled molecule deoxyribonucleic acid (DNA). Genes contain the instructions to make proteins, molecular laborers that serve as building blocks of cells, control chemical reactions, or transport materials to and from cells. The proteins produced in a human cell determine the function of each cell, and ultimately, the function of the entire body.
In a cancerous cell, permanent gene alterations, or mutations, cause the cell to malfunction. For a cell to become cancerous, usually three to seven different mutations must occur in a single cell. These genetic mutations may take many years to accumulate, but the convergence of mutations enables the cell to become cancerous.
CAUSES OF CANCER
Scientists do not fully understand the causes of cancer, but studies show that some people are more likely to develop the disease than others. The incidence of cancer varies enormously among different regions. The highest death rate from all cancers in males is 272 per 100,000 men in Hungary while the lowest death rate of 80 men per 100,000 is found in Mauritius, an island off the coast of eastern Africa. For women the highest cancer rate is 140 per 100,000 women in Denmark compared to only 63 per 100,000 women in Azerbaijan in western Asia. The figures for the United States are 156 per 100,000 men and 108 per 100,000 women. For particular cancers, the difference between countries may be as high as 40-fold. Differences also occur within populations. Cancer rates vary between sexes, races, and socioeconomic groups, for example.
Scientists called epidemiologists study particular populations to identify why cancer rates vary (see Epidemiology). One method they use is to compare behavior and characteristics such as the gender, age, diet, or race of cancer patients to those of healthy people. Population studies provide useful information about risk factors that increase the likelihood of developing cancer.
TYPES OF CANCER
More than 100 types of cancer develop in the various organs in the body. Cancers are described according to where in the body the cancer originated, what type of tissue it originated in, and what type of cell it started in. For example, breast cancer describes any cancer that originated in the breast. If the cancer spreads to a new organ, such as the lungs, the tumor is called metastatic breast cancer, not lung cancer.
Each organ in the body is composed of different types of tissue, and most cancers arise in one of three main types—epithelial, connective, or blood-forming tissue. Carcinomas are cancers that occur in epithelial tissues—the skin and inner membrane surfaces of the body, such as those of the lungs, stomach, intestines, and blood vessels. Carcinomas account for approximately 90 percent of human cancers. Sarcomas originate in connective tissues—such as muscle, bone, cartilage, and fat—that support and connect other parts of the body. Much rarer than carcinomas, sarcomas account for less than 2 percent of all cancers. Leukemias develop in blood cells, and lymphomas originate in the lymphatic system. Combined, these cancers of the blood-forming tissues account for about 8 percent of all human cancers.
Cancers are further identified according to the type of cell affected. For example, squamous cells are flat, scale-like cells found in epithelial tissue. Cancers that originate in these cells are called squamous cell carcinomas. Adenomatous cells are glandular or ductal cells, and carcinomas that originate in these cells are called adeno-carcinomas. Sarcomas that develop in fat cells are called lipo-sarcomas, and those that develop in bone cells are called osteo-sarcomas.
