My understanding is most people get cancer cells regularly. Possibly every day. The immune system clears them out naturally. The question is how old is a cancer before it becomes a threat worthy of analysis. Obviously one cell is probably not interesting. I think there's evidence even cancers that are large enough to be visible to the naked eye are not typically dangerous. If 99% are harmless, what is the point in early detection? It's an expensive test and expensive doctors visits to mitigate a 1% risk. It's interesting from a research perspective to be sure, but not as a standard of care.
We don't generally treat neoplasms, because we get lots of them, most are of no consequence, and treatments are damaging. We care about the malignant neoplasms where the biological cost of treatment is outweighed by the cost of allowing the malignancy to remain.
If you can reliably distinguish between those malignant neoplasms and "any growing neoplasm in the body", collect your Nobel and enjoy your well-earned message board karma from winning this debate. Since you can't, what you're really doing here is begging the question.
It's not about superstition or fear, it's about resource allocation and common sense. Medical services are finite. Screening and continuous monitoring of every potential tumor in everyone would be crazy time consuming and incredibly wasteful. So let's not.
EDIT: Just to be clear, the idea of accurate early detection is of course a good one. But as of today it is just not viable.
Along with better early detection, aren’t we trying to increase the tests’ accuracy?
If we have 2-3 additional years to monitor and treat a cancer, we have more options.