In patients with advanced stage lung disease, it is beneficial to evaluate candidacy for immunotherapy without invasive biopsy testing. Lou et al performed a concordance study to evaluate formalin fixed cell blocks compared to lung tumor resections using a PD-L1 22C3 IHC pharmDx™ assay and found strong concordance between pathologists and HALO image analysis software. Future research will focus on clinical validation by assessing the clinical benefit from immunotherapy following PD-L1 immunohistochemistry on cytology specimens.