Agree with Miss Molly. My thoracic surgeon said biopsies are good for positive results but they are not accurate for negative. It has to do with the "sampling" process. It's too easy to grab a piece of tissue that doesn't have cancer cells even though there's an active tumor.
I've had a few lung tumors, three cancerous and one benign so I think I can give you some advice.
First of all, I was diagnosed with two lung tumors, one in the bottom of each lung. They were both removed by wedge resection (using a VATS procedure) because of their location. Then about 10 months later I had something
show up in my right lung. It was also removed by wedge resection (VATS again), but it turned out to be a benign granuloma, so no cancer whatsoever. Then a year later I had another something
show up in my left lung. That time the entire lower lobe was removed, again with a VATS procedure.
The difference in the latter two cases is that my CEA did not increase
with the benign granuloma. What made them think it was cancer was that it was growing fairly quickly. But, when the next one appeared, my CEA started going up -- 1 point every few months. My docs and I felt very strongly that it was a lung met so we didn't even bother with a biopsy. The good news is that I've been clear since then and that was 4 years ago!
I'm assuming they can't do a wedge resection because of your lung met's location. In that case, see if the surgeon can try to remove it with VATS. Your pain level and recovery will be a lot faster. You stand a good chance of returning to your NED status after this surgery (and a few months of chemo) so stay strong and look at this as just a little bump in the road!
Also, if you need any advice about the surgery itself, feel free to PM me or ask here. One other thing, in case it matters to you: I am a runner/hiker/mountain climber (in other words, very physically active), and no one would know about my lung surgeries based on my athletic performance. I got all my lung capacity back in a year of training.
Hope this helps!