I think the easy answer here is that there are not. Cancer in humans happens when the cells do not behave like they should, and divide uncontrollably and in weird ways. Since whatever is good for the body happens usually, and cancer is a state of these uncontrolled cells, it is unlikely they would ever do any good to the human body as a whole.
There are some science fiction stories I’ve seen about people who become immortal and can regenerate limbs through cancer-like diseases, but they are not real and this could not work. What is interesting though is that some creatures, for example the salamander, can actually re-grow whole limbs if they are removed! Humans cannot do this, but it would be really awesome of they could!
In salamander, this growth is not due to cancer though. So no, for no reason would cancer be good I think!
Yup I agree with Daz. Cancer really is just occasions of when our bodies go wrong spontaneously or its caused by a virus.
But some people (but very very few) count cancer as a blessing! I know strange right. But it often makes people realise that they need to take care of themselves better (our body is a temple of course) if they want to keep living. Or say some people who get a cancer scare, say like a mole on their skin that starts growing, will become much more aware of the damage that sun can do to their skin so in future will take better precautions.
This answer makes me feel like i’m giving cancer an excuse. But I’m totally not!
Great question though as we know that some bacteria are good for us and some or bad so it seems acceptable that a certain type of cancer could be too!