Lump on my right collar bone

I have a lump on my right collar bone. No pain at all just swollen bone. I went to my doctor and she had it x-rayed and then called the next day and told me to schedule a cat scan. Why would she want a cat scan?

It doesn’t mean she saw something worrisome (yet). The scan is for more detail. I think its our insurance that says they won’t pay for scan, until after doctor has tried x-ray first. They always do that w me. let us know what happens.