HHLA2 and neoplasm: Overall, HHLA2 expression was more prevalent than PD-L1 expression (56% vs. 25%, p = 0.003), and within tumor specimens a higher proportion of cells, greater than 25% of the tumor volume, stained positive for HHLA2 compared with PD-L1 (21.4% vs 0%, p < 0.001).