Welcome to our forum. The first thing you'll hear from our Lungevity Family here is to wait until you get a solid diagnosis before you let your thoughts get away from you. The second thing is to NOT go on Google to see what it knows. Data for LC is changing all the time as treatments and outcomes are improving and published data is averaged over a 5-year period so it does not reflect the most recent data on positive outcomes.
Now, let's talk about that 3cm. 2.54cm=1inch so you are speaking about a relatively small growth, and yes it could be a nodule or any number of things including a tumor. But, until you have other tests (biopsy, PET scan, etc.) you won't really know what this is until the tests are done and then you can learn if treatment is necessary or not. I do understand your fear; my Mom and Dad both passed from cancer and it seems to run in my family. When I did learn of my diagnosis (Mar 2019) I was convinced that I'd be dead by the end of the year. In my case I had surgery and recovered well and am NED (No Evidence of Disease). So there is proof from me and others here that even with a positive diagnosis of LC there is more hope than any time in history, especially when it is detected early.
So, please try and take it easy. You need to work with your doctor on next steps and be ready for more than one test (biopsy, PET Scans, CT Scans, etc.). Also, feel free to ask any questions you have here and more than one of our members will have firsthand experience to help answer it for you.
And finally, just don't panic...you are a long way from your worst fear.