Login to Access Video or Poster Abstract: MP37-01
Sources of Funding: none

Introduction

Programmed death ligand-1 (PD-L1), a key target molecule for immunotherapy, is frequently overexpressed in several neoplasms. In the present study, we examined PD-L1 expression in pheochromocytoma because very few reports on this subject are available.

Methods

PD-L1 mRNA expression was compared across 184 pheochromocytoma, 492 prostate cancer, and 404 bladder cancer cases based on The Cancer Genome Atlas (TCGA). Furthermore, we enrolled 32 pheochromocytoma patients who were surgically treated at our hospital between June 2005 and February 2016. We conducted PD-L1 immunohistochemistry (IHC) using the SP142 assay. PD-L1 expression was scored at three diagnostic levels (0, 1, and 2).

Results

A comparison of PD-L1 mRNA expression based on the TCGA revealed that PD-L1 expression was significantly higher in pheochromocytoma than in bladder cancer and prostate cancer (p < 0.001). _x000D_ The SP142 assay of our 32 surgical pheochromocytoma cases revealed that the prevalence of a PD-L1(+) expression (IHC score 1 or 2) in tumor-infiltrating immune cells (TICs) was 25% (eight patients) and that in tumor cells (TCs) was 28.1% (nine patients). The tumor diameter was significantly different between PD-L1(+) TIC patients (3.36 ± 0.35 cm) and PD-L1(-) TC patients (5.37 ± 0.50 cm, non-paired t-test: p = 0.044). In our cohort, there were two cases of malignant pheochromocytomas but none of them were PD-L1(+). _x000D_ _x000D_

Conclusions

PD-L1 expression is relatively higher in pheochromocytoma than that in bladder cancer and prostate cancer based on TCGA. The SP142 assay of our 32 surgical pheochromocytoma cases revealed that the tumor diameter in PD-L1(-) TIC cases was larger than that in PD-L1(+) cases. Further, there were no PD-L1(+) cases of malignant pheochromocytoma._x000D_ These findings suggest that PD-L1 expression in pheochromocytoma is relatively common and that PD-L1(+) expression in pheochromocytoma may not be associated with tumor aggressiveness._x000D_

Funding

none