Yosef Karo

“ Two pustules facing each other from two lobes is kosher. But a pustule against a Tinri (a hard rock-like growth) is Treif, since the Tinri is hard and would puncture the pustule facing it (M"K) . But a pustule and a Tinri adjacent is kosher (D"A) . 4 A pustule found on the lower parts of the lung, the practice is we forbid them if there isn't some amount of flesh surrounding all sides (specifically [excluding] Boah, but Tinri is flesh in the lower parts of the lung) (D"A, MHR"Y and H"M) .
And Shipulei (lower parts) means the lower bronchioles or the lobe, but not the cuts between the lobes. ”

“ Rema: And some say that any place that has Chidud (rigidness) is called Shipulei Reah (MHRY"W, SM"K and Kol Bo) , therefore we should rule treif even higher up, where the lung is clung to the spine or it's against the cuts of the lobes, as the lungs is still Chad there and called Shipulei. But against the lobes it's kosher, as there wouldn't be Shipulei there, for there the lung is wide (B'bedikot) . This should be conducted according to the custom. And if there's no line of flesh surrounding it we inflate it and feel on the side of the Boah ”