For the cancer I had on my tongue, I had a lesion underneath my tongue for 10 years. It was a small white lesion and my dentist kept an eye on it and told me if it ever changed we would have a biopsy done. I moved away and went to a different dentist and he said the same thing. It was at the 10 year mark that the lesion changed and began to hurt and my dentist said, "It doesn't look like cancer." and he shrugged his shoulders...but he requested a biopsy be done as soon as possible (thankfully).
I went to an oral surgeon for the biopsy and he said the same thing, "It doesn't look like cancer...but you're here for the biopsy, so we'll do it." Not even a week later, I got the call to come in immediately and it was cancer. The doctor said, "I'm never wrong, but this time I'm wrong, it is cancer." He was truly shocked he was wrong.
The lesion changed from just white to having redness around it. The pain was a constant throbbing that medicine could not take away.
I was fortunate we caught it early and only had to have part of my tongue removed (instead of the entire thing).
When the cat scan was done to examine my head and neck to see if the cancer had spread (it hadn't), they found a suspicious nodule on my thyroid. That turned out to be cancer #2. No pain with that. My thyroid was a mess though and I had gained a lot of weight because my body wasn't properly metabolizing food.