Immunotherapy targeting the PD-1/PD-L1 pathway represents a new therapeutic paradigm and a promising treatment option for advanced non-small-cell lung cancers, melanoma, and more recently, gastric and gastroesophageal carcinomas. As the role of PD-L1 IHC testing in the diagnostic work-up of solid tumors continues to expand, practicing pathologists are playing an increasingly larger role in test selection and integration of these molecular data into their reports, according to Dr. Larissa Furtado, who is teaching a course PD-L1 testing at CAP19 (www.capannualmeeting.org). In this CAPcast, Dr. Furtado provides an overview of PD-L1 testing, as well as how pathologists can confront the challenges related to implementing PD-L1 IHC testing into their laboratories.