A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread. Some types of cancer do not form a tumor. These include leukemias, most types of lymphoma, and myeloma.
A carcinoma begins in the skin or the tissue that covers the surface of internal organs and glands. Carcinomas usually form solid tumors. They are the most common type of cancer. Examples of carcinomas include prostate cancer , breast cancer , lung cancer , and colorectal cancer. A sarcoma begins in the tissues that support and connect the body.
A sarcoma can develop in fat, muscles, nerves, tendons, joints, blood vessels, lymph vessels, cartilage, or bone.
Leukemia is a cancer of the blood. Leukemia begins when healthy blood cells change and grow uncontrollably. The 4 main types of leukemia are acute lymphocytic leukemia , chronic lymphocytic leukemia , acute myeloid leukemia , and chronic myeloid leukemia.
Lymphoma is a cancer that begins in the lymphatic system. The lymphatic system is a network of vessels and glands that help fight infection.
However, the theory that cancer was caused by an excess of black bile continued to prevail in the 16th century. Cancer was considered incurable, although a wide variety of pastes containing arsenic were formulated to treat its manifestations. In the 17th century, the old theory of disease based on bodily humors was discarded when Gaspare Aselli discovered the vessels of the lymphatic system and suggested abnormalities of lymph as the primary cause of cancer.
Rejecting the 17th-century theory about the cause of cancer was the French physician Claude Gendron. He concluded that cancer arises locally as a hard, growing mass , untreatable with drugs, and must be removed with all its "filaments.
Two 18th-century French scientists, physician Jean Astruc and chemist Bernard Peyrilhe, conducted experiments to confirm or disprove hypotheses related to cancer. Their efforts, however absurd they seem in retrospect, established experimental oncology , the science of seeking better diagnosis , treatments and understanding of the causes of cancer.
During this period, environmental cancers were reported, and hospitals specializing in cancer care were opened. In the late 19th century, the development of better microscopes not only helped document and define disease-causing organisms, but also made possible the examination of cells and cellular activity. Study of cancer tissues and tumors revealed that cancercells were markedly different in appearance than normal cells of surrounding tissue or the cells from which they originated.
Researchers began to focus on questions such as the origin of cells and the relationship of disease to the behavior of a cell. This is a mutation. It means that a gene has been damaged or lost or copied too many times. Mutations can happen by chance when a cell is dividing. Some mutations mean that the cell no longer understands its instructions. It can start to grow out of control. There have to be about 6 different mutations before a normal cell turns into a cancer cell. What is cancer and how does it start?
Cancer Research UK ! Content not working due to cookie settings. View a transcript for the video about what is cancer and how does it start. It can take many years for a damaged cell to divide and grow and form a tumour big enough to cause symptoms or show up on a scan. They can also be caused by the processes of life inside the cell.
When we hear about some of the causes of cancer, it may seem as if cancer is a recent ailment. Yet we've been learning that cancer has afflicted people for centuries, and as far back as the written word. Let's take a look at some of what we know about the history of cancer, and how both the ideas of causation and treatments have changed over time. The word "cancer" came from the father of medicine: Hippocrates, a Greek physician.
Hippocrates used the Greek words carcinos and carcinoma to describe tumors, thus calling cancer "karkinos. Although Hippocrates may have named the disease "cancer," he was certainly not the first to discover the disease. The history of cancer actually begins much earlier. The world's oldest documented case of cancer hails from ancient Egypt in BC. It was treated by cauterization, which destroyed tissue with a hot instrument called "the fire drill.
There is evidence that the ancient Egyptians were able to tell the difference between malignant and benign tumors. In Ancient Greece, much less was known about the human body than what is known today, of course. For example, Hippocrates believed that the body was composed of four fluids: blood, phlegm , yellow bile , and black bile. He believed that an excess of black bile in any given site in the body caused cancer.
This was the general thought of the cause of cancer for the next 1, years. Autopsies done by William Harvey in paved the way to learning more about human anatomy and physiology. Blood circulation was discovered, opening the doors for more research on diseases. It wasn't until that autopsies were performed to research the cause of death in ill patients. Giovanni Morgagni of Padua was the first to do such autopsies. The lymph theory developed in the 17th century, replacing Hippocrates' black bile theory on the cause of cancer.
The discovery of the lymphatic system gave new insight into what may cause cancer.
0コメント