This is a form of hypochondria – where people think they are ill, but have nothing physiologically wrong with them. And apparently some women who have had a breast removed for cancer treatment (called a ‘mastectomy’) can feel phantom pain in the removed breast:
However, you can’t induce cancer through willpower, as the causes are (aside from lifestyle choices) generally out of our control. Fantastic question – I had never thought of phantom cancers. Well done!
I don’t think I have ever heard of “phantom” cancer. Apart from that, there are a lot of studies trying to investigate if there is a link between stress and cancer, but most scientific studies have found that stress does not increase the risk of cancer. The way that stress could lead to cancer, it’s maybe more an indirect one, because if you are stressed you are more likely to adapt more unhealthy behaviours, like drinking, smoking or over-eating that are all high risk factors for developing cancer