LAUSR

Immunotherapy based on disruption of the PD‐1/PD‐L1 axis is standard of care for many high stage malignancies including melanomas, non‐small cell carcinomas of the lung, triple negative breast carcinomas, and squamous cell carcinomas of the head and neck. Eligibility for immunotherapy requires immunohistochemical assessment of PD‐L1 expression. Currently, many high stage malignancies are diagnosed by cytology and cytologic material is the only specimen available for ancillary testing. Formal guidelines do not currently exist defining the optimal specimen type, antibody to be used or the best scoring system for cytologic material. Significant information has been published for PD‐L1 testing of pulmonary specimens but much less data exists for the reproducibility, accuracy and best practices for material obtained from other body sites and types of malignancy.