Any freak stories where someone switched their diet and their cancer dissipated and didn't know it?

There undoubtedly are, but the stories would anecdotal and have no basis in evidenced based scientific medicine—and should not be seen as any validation that diet therapy has any therapeutic value in cancer treatment whatsoever.

I agree with @Rarebear but if you want one well, I noticed a benign tumor in my mouth pretty much disappear shortly after I changed my lifestyle pretty much including diet, but I tally that one up to coincidence.

One of my dad’s work colleagues had cancer and took the kernels that you find inside an apricot seed everyday for a few months, and his doctor was astonished that it had shrunken and disappeared.
I don’t know the exact details, but something about them containing cyanide apparently destroyed the cancer cells. You either believe it or not, but why would someone just lie about something like this? I don’t think you can completely dismiss these kinds of stories.

@Keep_on_running Your post made me read up on it. It seems there are articles that suggest that the kernels do show some promise in curing certain cancers or at least reducing their size. Good to know if I ever get cancer.

Look up Gerson Therapy.

@King_Pariah: a benign tumor would not be classified as cancer. Cancerous tumors are malignant. By definition, a benign tumor is not cancerous.