Is the argument then that scans are intrinsically error prone, as in the noise level is so high that even a team of highly trained radiologists can’t accurately determine if cancer is present from a scan?
Relatedly, for many types of brain tumors, you simply don't know what exact kind of tumor it is until you actually do a biopsy (= you undergo surgery). This can be important information ("how aggressive is it?"), so in some hospitals it is common practice to send a tissue sample for identification and get back the result while the surgery is still going on.