What clinical and pathologic features do you use to discern whether >= 2 synchronous lung nodules, biopsy proven lung adenocarcinoma, are different primaries versus metastatic disease?

These cases are always discussed at a multi-disciplinary tumor board with a review of pathology slides from the operative specimen. In some cases, there are clearly different morphologies or levels of differentiation. These can be initial clues, but not definitive to determine synchronous primaries vs. metastatic lesions. At our site, we do routinely perform NGS on both specimens and this has become more of a default approach to these cases. That information is sometimes incorporated in initial ...