The novel 19G endobronchial USS (EBUS) needle samples processed as tissue "core biopsies" facilitate PD-L1 and other biomarker testing in lung cancer specimens: case report and the view point from the Respiratory Physician and the Pathologist.

The immunohistochemical expression of Programmed Death Ligand (PD-L1) predicts responses to PD-1/PD-L1 inhibitors in non-small cell lung cancer (NSCLC). PD-L1 testing is currently only recommended on tissue specimens; however, in many patients, cytology samples are the only specimens available. The introduction of the novel 19G "core-biopsy" needle has revolutionized the utility of endobronchial USS-guided biopsy (EBUS) by providing solid tissue "microbiopsies" rather than traditional liquid cytology samples. We report a case of metastatic adenocarcinoma with the only accessible site of biopsy being a hilar lymph node. Using the 19G core-biopsy needle and processing the microbiopsy samples in formalin provided more material for predictive biomarker testing, including PD-L1 immunohistochemistry, when traditional processing was inadequate. This case highlights the need for close multidisciplinary discussions between the pathologist and the respiratory physician regarding emerging biomarkers and novel biopsy techniques to obtain maximum utility of the tools and avoid repeated procedures for the patient.