Table 3. Difference of PD-L1 protein expression in different differentiation groups.

Differentiation	Variable	p value	ρ value
Well~ medium
	Age	0.045	−0.081*
	Sex	0.000	−0.158**
	Histological type	0.000	−0.226**
	Tumor maximum diameter	0.010	0.146*
	Tumor (T)	0.027	0.127*
	Region lymph node (N)	0.000	0.280**
	Metastasis (M)	0.000	0.246**
	Clinical stage	0.000	0.306**
Poor
	Age	0.017	0.142*
	Tumor (T)	0.048	0.200*
	Region lymph node (N)	0.029	0.219*

Note: ρ refers to Spearman coefficient. ρ value greater than zero means a positive correlation and less than zero means a negative correlation.