Table 2.

Differential expression of PD-L1 in primary tumor site and metastasis or subsequent specimen in malignant mesothelioma.

PD-L1 expression		Overall*		Epithelioid MM		Biphasic MM
Initial specimen	Subsequent specimen / metastasis	Number (%) of MM at different time points (N = 58)	Number (%) of primary MM and metastasis (N = 16)	Number (%) of MM at different time points (N = 46)	Number (%) of primary MM and metastasis (N = 14)	Number (%) of MM at different time points (N = 9)	Number (%) of primary MM and metastasis (N = 2)
Concordant
Negative	Negative	23 (40)	7 (44)	20 (43)	7 (50)	3 (33)	0
Positive	Positive, expression score same as in initial specimen	18 (31)	2 (12)	14 (30)	1 (7)	2 (22)	1 (50)
Discordant
Negative	Positive	6 (10)	3 (19)	5 (11)	3 (21)	0	0
Positive	Negative	5 (9)	2 (12)	4 (9)	2 (14)	1 (11)	0
Positive	Positive, expression score higher than in initial specimen	1 (2)	2 (12)	1 (2)	1 (7)	0	1 (50)
Positive	Positive, expression score lower than in initial specimen	5 (9)	0	2 (4)	0	3 (33)	0

^*2 (of 2) sarcomatoid mesotheliomas had concordant PD-L1 expression scores in the initial specimen and subsequent specimen; 1 mesothelioma had discordant (negative to positive) PD-L1 expression scores in the initial specimen (well differentiated papillary mesothelioma) and subsequent specimen (epithelioid MM). MM, malignant mesothelioma