Heterogeneity of PD-L1 expression in lung adenocarcinoma metastasis is related to histopathological subtypes

Abstract Objectives The heterogeneity of PD-L1 expression and its relationship with histopathological subtype has recently been shown on primary tumor but has not been evaluated on metastases. The aim of our work is to analyze PD-L1 expression within each histopathological pattern on resected metastases. Material and Methods 136 patients were included in this retrospective study. Immunohistochemistry was performed with 22C3 laboratory-developed test. The Tumor Proportion Score was evaluated on each subtype. Results The most frequent major histopathological subtype was solid (n = 69, 50.7%), followed by acinar (n = 37, 27.2%), micropapillary (n = 14, 10.3%) and papillary (n = 10, 7.3%). Mean percentage of PD-L1 expression for each subtype was at 28+/-4.8% for solid subtype, 5.3+/-1.9% for acinar subtype, 5+/-1.9% for papillary subtype and 23.6+/-4.1% for micropapillary subtype. Mean percentage of PD-L1 expression was different between solid pattern and acinar pattern (p