When would you consider biopsy for an incidentally noted, PET negative, solid, solitary pulmonary nodule that is >8mm in size?

No, probably not. The whole point of a PET scan is to use it for its negative predictive value (which is very high for a nodule that is solid, and large enough). I'd like to know just how large it is because smaller nodules (e.g. just at or above the 8 mm size threshold we all perseverate on) can be...