Table 2.

Histological characteristics of typical carcinoid tumors with programmed death ligand 1 (PD-L1) expression.

PD-L1 expressiona	PD-1 expressionb	Ki-67 (%)	Tumor size (cm)
95	0	1	1.0
37	0	<1	1.0
14	2	1	0.9
5	0	<1	2.0
4	177	2	3.0
4	3	4	1.3
4	1	2	2.0
2	1	<1	1.5
1	1	9	1.5

^a% of tumor cells expressing membranous PD-L1 staining; ^bnumber of intratumoral PD-1 labeled lymphocytes per mm².

PD-1, programmed death protein 1.