Are CT Scans still effective without dye or contrast?

Will a CT without contrast/dye still pick up tumors? A tumor was incidentally found on my MRI so I’m having further scans, but they did not use contrast with my CT scan… and they usually always do. I’m afraid that the CT will not pick up on the tumor(s) and I really want this taken care of, as I am a cancer survivor and I have most of the risk factors that this is cancer.