Formalin fixation on HER-2 and PD-L1 expression in gastric cancer: A pilot analysis using the same surgical specimens with different fixation times

Table 1 Clinicopathological characteristics and immunohistochemistry results according to used formalin solution n (%)

	All cases (n = 32)	10% formalin (n = 22)	1% NBF (n = 10)	P
Age (mean ± SD)	74.5 ± 7.8	73.3 ± 8.0	77.1 ± 7.0	0.2020
Gender				0.7731
Male	18 (56.3)	12 (54.6)	6 (60.0)
Female	14 (43.7)	10 (45.4)	4 (40.0)
T-Stage				0.6793
T1b2	6 (18.8)	3 (13.6)	3 (30.0)
T2	9 (28.1)	6 (27.3)	3 (30.0)
T3	5 (15.6)	4 (18.2)	1 (10.0)
T4a	12 (37.5)	9 (40.9)	3 (30.0)
Lauren's classification
Intestinal	18 (56.2)	12 (54.6)	6 (60.0)	0.7731
Diffuse / mixed	14 (43.8)	10 (45.4)	4 (40.0)
HER-2 IHC
Complete negative1	24 (75)	18 (81.8)	6 (60.0)	0.1966
Final positive by DISH	5 (15.6)	2 (9.1)	3 (30.0)	0.1311
PD-L1 positivity
Cut off 1%	20 (62.5)	14 (63.4)	6 (60.0)	0.8439
Cut off 10%	13 (40.6)	8 (36.4)	5 (50.0)	0.4666
Cut off 50%	7 (21.9)	4 (18.2)	3 (30.0)	0.4535

¹The cases that all four specimens of different fixation time were assessed as score 0.

IHC: Immunohistochemistry; NBF: Neutral buffered formalin; DISH: Dual color in situ hybridization; HER-2: Human epidermal growth factor receptor 2; PD-L1: Programmed death-ligand 1.