[thaumasiotes]

In medical school, one of my mother's classes had an exercise one day which took this form:

Here are a bunch of slides of prostate samples. Find the cancerous one.

This led to the teacher getting so many questions about whether the slide someone was currently looking at was the cancerous one that he was forced to interrupt the class to make this more general announcement:

There's a bit of cancer in everyone's prostate. Find the slide with obvious cancer.

[copperx]

Surely the slides were of men of an advanced age, right? Otherwise that statement is false.

[Dalewyn]

I'm not a doctor, but my understanding has been that we all have cancer cells at any given point in time. Consider how many cells inside you are undergoing cell division; errors in cell division are where cancer cells come from.

The question is whether your body sees and kills the cancer cells; most of the time it does, which is why most of us can live pleasantly for most of our lives despite errors cropping up silently. What we term cancer are the cancer cells that slipped past our body's defences, growing into masses that cause no end of grief.

To put it in computer terms, it's like error correction in HDDs and SSDs and ethernet connections. Errors are inevitably going to occur while data is in transit, but they are of no concern so long as error correction and other such mechanisms can correct and recover. The errors do become a concern when they start slipping past such mechanisms, however.

[zkirill]

This is my understanding as well and my favorite protein, p53 [1], is responsible for hunting down cancerous cells. From what I remember reading in Robins Basic Pathology, it takes many steps for a cell to evolve into cancer and our body has ways to reduce the probability at each step. The most fascinating topic to me is how someone's lifestyle and environment affect their body's natural cancer defence mechanisms. We can do many things to stack the odds in our favour, but sometimes the odds are still not in our favour. Should we strive to minimize the chance by adjusting our lifestyle and changing the environment, or strive for some kind of balance?

[1] https://en.m.wikipedia.org/wiki/P53

[pfdietz]

Elephants have 100x as many cells as a human does, live about as long, but have about 1/2 the chance of dying of cancer. Why? A big part is that each elephant cell has ~40 copies of the p53 gene.

[hawk_]

Before anyone thinks of increasing p53 in human bodies to prevent cancer keep in mind that it can cause premature aging.

[pfdietz]

I'm sure elephants have all sorts of compensatory mutations so they can live with so many copies of the gene.

[Dalewyn]

>Should we strive to minimize the chance by adjusting our lifestyle and changing the environment, or strive for some kind of balance?

That is as much a philosophical question as it is biological, and one where the answer will vary by who is asked.

Personally, I will say this: If you're miserable while endeavouring to prevent cancer (or any other disease), that's putting the cart before the horse. The goal is, presumably after all, to live happily.

[copperx]

That's my understanding too. But we're talking about cancer that can be observed on a slide. At that point, that's beyond the error correction mechanisms AFAIK.

[thaumasiotes]

Why do you think that?

[copperx]

I don't believe every person of every age has observable cancer that can be seen on a slide.

[thaumasiotes]

You're probably correct as to babies. But the prostate gland is extremely cancerous and my assumption would be that that tendency begins at either birth or puberty. The exponential function spends the entire infinite length of the negative x-axis rising from 0 to 1; think about the growth of cancer in your prostate gland that way.

I would not expect a man in his late 20s to fall into the category "men of an advanced age". But I would be unsurprised to learn that there was visible protocancer in a sample of his prostate.