However, IHC-based detection of PD-L1 expression is constrained by preanalytical and analytical variability including heterogeneity in antibody clones, scoring methodology, and intrinsic biological variation in PD-L1 expression due to the type of specimen analyzed (surgical resection vs. biopsy, primary tumor vs. metastasis, archival vs. fresh frozen) as well as prior treatment status. The gene discussed is CD274; the disease is neoplasm.