There is probably a disproportionate amount of texts describing the presence of a tumor on a scan than texts describing what a normal scan would look like. So this is expected. But I think that is not the purpose of a LLM. There should be a classification algorithm detecting the presence or not of a tumor and then a a LLM can be used to generate a description of it or why the scan is normal.

And I don't know any, but there is probably already tools to help radiologists, what they call their "own AI".