I didn't even have a biopsy before surgery. My nodule/tumor was right around 1 cm, but it had grown, plus had a spiculated appearance, so the recommendation for surgery was based on that. They did remove a section of lung and examine it during the surgery, which confirmed the cancer, and the surgeon therefore removed the entire lobe.
In your case, apparently the pathologist was able to determine it was adenocarcinoma, but not much else. That might be based on the quality of the sample they were able to take in the biopsy--it might not have had enough cells to draw too many conclusions. And actually, that's more than enough information, as augmented with the PET/CT scan results, to make an initial treatment plan.
But nothing is ever carved in stone with these things. If you have surgery, they will remove lymph nodes near the affected lobe for later examination. If they find any cancer cells then, it will indicate the cancer has started to spread and they will adjust treatment accordingly. Not all cancerous lymph nodes show up on a PET/CT.
For me, the most helpful mindset to keep is to stay flexible, hoping for the best but knowing things can take a turn unexpectedly. I never assume I'm DEFINITELY in the clear, for good.