Cell Replacement & Growth: Normal and Abnormal
Cells normally grow to replace older cells, which continuously die and are absorbed by the body in a very orderly fashion. That way, in an adult, most organs and tissues stay more or less the same size. In order to grow new cells, the DNA is reproduced and chromosomes divide by an orderly process called mitosis.As you will learn, when cancer cells grow, they lose control and reproduce and divide very rapidly in a dis-orderly fashion. Thus they are often said to have a high “mitotic rate.”
When cancer develops in an organ or tissue, the cells begin growing in an un-controlled fashion and are unchecked by your body's usual immune defense mechanisms. The reason they start mis-behaving is based on very complex interactions between DNA/genes and regulating proteins which support and interact with genes.
Proteins as Genetic Switches
Some proteins around the DNA turn genes on and some turn various genes off, in a highly orchestrated way. When something goes wrong with this based on environment or other unknown factors, abnormal cell division and growth begins. Up to 85% of ovarian cancer cases arise by this mechanism. This is called sporadic ovarian cancer.In the remaining 15% to 20% of cases, ovarian cancer occurs as a result of abnormally coded genes passed on through generations. This is called familial ovarian cancer. Most of the known abnormal genes for ovarian cancer risk are located in what are known as the BRCA loci. If genetic counseling determines that there is a strong family history, BRCA gene abnormalities can be tested for.
Unsuppressed Growth
Normal cells divide only enough to replace those that die or to repair injuries, then stop dividing. Cancer cells have lost this restraint due to the DNA/gene instructions the cell's biochemical machinery gets and keep dividing and piling up on each other.The mass of cancer cells will eventually become large enough to cause symptoms and to become detectable as a lump or a mass on a X-ray or scan. Usually the smallest lump that can be detected by feeling it or by scan is the size of a pea, and that already contains about 100 million cells.
Assuming cancer starts as a single abnormal cell, and that cell divides and each cell that is produced keeps dividing and so on, the amount of time to get to a pea size mass can take many months to years. At some point, the cells can grow directly into adjacent tissues and organs, or break into into tiny blood vessels or lymphatic vessels and spread to lymph nodes and other parts of the body. These processes are called invasion and metastasis.
