I wouldn't be too surprised to learn that cancer is in fact over-mutation.

Caused by either natural defects in the genetic coding that lead to hazardous mutation (pretty rare I guess)

Not at all rare. This is why your family medical history is important-- if there is a high incidence of a specific cancer in your family, there is a higher chance that you carry a genetic mutation which renders you more vulnerable to it. (You could also share an environmental hazard, which is why genetic testing looks heavily at blood relatives raised in different places.) It's also why some diseases (Tay-Sachs, sickle cell, etc.) can run in specific ethnicities, regardless of place of residence.

, or unhealthy influences, like smoking, chemical pollution, radiation, ..., which sadly is all too common.

All of the above. Most cancers are the result of multiple defects-- your body has dozens of cancerous 'events' per day, but it's generally capable of detecting the aberrant cells and telling them to self-destruct. Only when the aberrant cell is either exceptionally hardy, or when the 'correction' mechanism (Google TP53 for an aexample) has also been damaged.

valguarnera@carrionfields.com