If cancer grows into a structure inside of you, would it likely result in excrutiating pain?

Answer 1

its very possible. invasive cancer like bone cancer is extremely painful. other cancers can go unnoticed for a very long time: colon cancer, ovarian cancer, breast cancer.

Answer 2

I knew an older lady who had bone, liver, and pancreatic cancer--never once complained of pain. She didn't last long though. Some seem to have more pain than others. Some cancers seem to cause little to no pain.