It doesn't all have to do with how visible the tumor is, though. Mine (and Cathy G's too) was right there on the edge of my tongue--quite visible--and the dentist and hygenist even commented on it on a visit before it had grown large enough for them to get more concerned but didn't ask me how long it had been there or tell me to get a biopsy. And my GP also, even when it was quite large, didn't think it could be cancer. Later he said apologized--he'd just never seen a tongue cancer before (and I'd say he's in his 40s). There definitely needs to be better training on this.

As for poeple "knowing" when something "isn't right with their body", I wish this were true. Unfortunately many cancers are so stealthy people have no idea until they are well advanced because they feel absolutely fine. In other cases, such as mine and I think Cathy's, we did have pain and may have wondered if something wasn't right but when it is dismissed by doctors who you would expect would know if there were a problem, it's easy to dismiss it yourself!

Nelie