Hi Beth,
Sorry you need to be here, but glad you found us. Sometimes the diagnostic process for this disease alone can make one crazy. It needs to be exacting, definitive, and accurate. I can tell you know that while CT and PET Scans have a place in diagnosis the definitive diagnosis is made via a biopsy. So shadows, nodules, and other abnormalities could be indicative of cancer the biopsy is the only definitive tool to determine malignancy, and other factors (i.e., genetic markers). Please take a look at "Navigating Your Diagnosis" and you'll see the difference between screening, markers, and definitive diagnosis. You need to get to the biopsy stage for a true diagnosis. Along with that you also want to know what genetic markers may be impacting the findings. Once you have that data settled you will begin to look at what treatments are available to help your Grandmother. So while it may be possible or even probable that it is cancer we don't pull the trigger on anything until it's been diagnosed.
I'm not fully familiar with the UK health system but others here are and I'm sure that you'll hear from them soon. In the meantime please keep us updated and ask any other questions you may have.
Lou