Pathologic regression of tumor in 20 non-small cell lung cancer resection specimens following neoadjuvant blockade of Programmed Death 1 (PD-1) with 2 doses of Nivolumab. The gray horizontal line indicates the threshold for major pathologic response (90% regression). AC= adenocarcinoma, LN= lymph node, PD-L1= Programmed Death Ligand 1, PR= partial response, RECIST= Response Evaluation Criteria in Solid Tumors, SCC= squamous cell carcinoma, SD= stable disease.5