Cells are the structural and functional unit of all living organisms. The human body has an estimated 100,000,000,000,000 cells. Each cell can independently take in nutrients, convert them into energy, carry out specialized functions, and reproduce as necessary. A sphere about one quarter of an inch in diameter contains an estimated 1,000,000,000 cells. Each cell has a different purpose - muscle cells which make movement possible, nerve cells which allow sensation, etc. Particular cells are organized into functioning structures called organs.
A cell is composed of a nucleus surrounded by the cytoplasm, all contained within a cell membrane. The nucleus contains the genetic material called the chromosomes. They control the heredity of each cell and are strung like beads on a necklace along the cellís DNA (deoxyribonucleic acid) in the cell nucleus. Genes control cell division and the repair of chromosomal defects. In a benign or malignant tumor, several of the genes regulating these processes are abnormal (mutated). Abnormal genes may be inherited or damaged by carcinogens, viruses, errors in cell division, or as yet unknown factors. Each pair of chromosomes is numbered and can be identified by special microscopic techniques. This is why you will hear references made to a certain specific gene or chromosome number when reading cancer research papers.
Every minute, it is estimated that 10 million of our human cells divide. This division is referred to as mitosis. There are over 200 types of cells in the human body that vary greatly in size, shape, and function. Usually, cell division, accompanied by growth and specialized development, takes place in an orderly pattern. But when a cell becomes malignant, it acts in profoundly abnormal ways. Instead of maturing and dying in a normal fashion, cancerous cells reproduce without restraint. Itís not that they divide faster, but that they never stop dividing, and they fail to mature. When removed from the body and placed in a laboratory dish with nutrients, they actually seem to be immortal.
If a cancer starts as a single cell and that cell begins to divide and if the volume of that mass of cancer cells doubles every 45 days, then it would take about 30 doublings for the mass of cancer cells to reach the size of a tumor about one quarter inch in diameter. This is the smallest mass that can be detected by examination, x-ray or scan. A cancerous tumor this size contains an estimated 100,000,000 to 1,000,000,000 cancer cells. It would only take 10 more doublings to reach a size considered fatal. Forty doublings would be 1,000,000,000,000 cells or about one kilogram (2.2 pounds) of cancer. As you can see by this process of cancer development, growth, detection, and fatality; early detection and treatment of a cancerous growth is important to survival.
Cancerous tumors cause problems because they grow and occupy space. They push on other structures and cause them to malfunction. This mass of cancer cells has to have a blood supply to survive, so it causes neighboring blood vessels to grow into it. These blood vessels are often faulty and break easily. Bleeding is one of the signs of cancer. The term for this new blood vessel growth is angiogenesis.
The spread of cancer happens in three ways:
Direct extension, where the cells literally grow into nearby organs.
Through the lymphatic system where cells from the original tumor break off and enter the lymph canals.
Through the blood stream.
Once this happens, these cancer cells migrate to many other distant sites and organs in the body. In this way, multiple growths occur, affecting many parts of the body, eventually causing multiple organs to fail. These growths are known as secondary cancers or metastasis. Organs or parts of the body that have a rich blood or lymph supply are the most likely sites for these secondary malignant growths to appear. Such organs include, the lungs, the liver, bone marrow and lymph nodes.
Cancerous cells have no nerves so they do not hurt. They can cause other structures to hurt because of the destruction or pressure on the normal structures. They require energy to grow and rob the body of the energy it needs for normal function. Many cancers, such as prostate cancer, grow slowly and may be present for many years before causing symptoms. Prostate cancer is rarely evident in men in their 40s, but by age 85 or 90, most men have some cancer cells in their prostate, although this condition is usually localized and not a serious medical problem. Cancer in children, on the other hand, tends to grow more quickly than in adults because childrenís body tissues generally grow rapidly.