He's got a tentative diagnosis of sarcoidosis; the initial biopsy was inconclusive.
Now they want to do serious exploratory surgery to get a bigger tissue sample to determine what's going on with his lungs (he's down to 50% or less of lung capacity). Assuming it does confirm sarcoidosis, it can be treated--and sometimes it responds after six months of Prednisone or something similar.
Or not. If it responds, he's told he could recover up to 70% of lung capacity.
If not, he'll be a candidate for lung transplant surgery.