CD274 and neoplasm: This trial was designed for extensive exploratory biomarker analysis to identify patient subgroups with response to atezolizumab that included: (1) tumor and immune PD-L1 expression, (2) nonsynonymous mutation burden rate, (3) TNBC molecular subtype, and (4) lymphocytes composition by multichannel immunofluorescence (eMethods in Supplement 2).