To summarize, there are four major phases of tumor formation. Each phase can take years to complete. The first one alone usually takes anywhere from 15 to 30 years.

The first phase occurs when normal cells mutate into tumor cells and begin dividing out-of-control. This may take place over successive generations of cells. When just the right mutations occur, the cells will divide and grow to a small tumor.

The second phase is called Carcinoma in situ. This phase is classified by the presence of a cancerous tumor that has not yet invaded other tissues. This phase usually lasts between 5-10 years and is limited by the nutrient flow to the tumor. If blood vessels can be induced to grow into the tumor (angiogenesis), the tumor will progress to the next phase, called the invasive stage.

The invasive phase can happen rapidly, requiring only a few months. However, in some cases it may take up to five years. This phase is dependent on the ability of the tumor to invoke nearby blood vessels to grow toward it and provide it with nutrients - commonly referred to as angiogenesis.

Metastasis, or dissemination to other tissues if the final pha

se. This phase has the same time period as the invasive phase, ranging from a few months to five years.

At each phase, the cancer can either progress further or altogether diminish. If you add each phase up, the average for the cell mutating events and cancer diagnosis is 20-50 years apart. This is why cancer mostly affects older people. Actually, half of all cancers are diagnosed after the age of 65.

A Few Checks and Balances... - Mutations must occur, but the cell must still live and divide. - DNA repair mechanisms must not be activated. - Our own immune system must not find the tumor and destroy it. - The tumor must get enough nutrients to continue to grow.

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