Table 1. Correlation of vascular invasion with patients’ clinicopathological features in primary esophageal squamous cell carcinomas.

Variable	Vascular invasion
	Training cohort				Validation cohort
	Cases	Absent	Present	P value*	Cases	Absent	Present	P value*
Age (years)				0.941				0.021
≤57.0†	118	56 (47.5%)	62 (52.5%)		112	54 (48.2%)	58 (51.8%)
>57.0	98	47 (48.0%)	51 (52.0%)		105	67 (63.8%)	38 (36.2%)
Gender				0.459				0.684
Female	64	33 (51.6%)	31 (48.4%)		48	28 (58.3%)	20 (41.7%)
Male	152	70 (46.1%)	82 (53.9%)		169	93 (55.0%)	76 (45.0%)
Location				0.028				0.159
Upper	10	3 (30.0%)	7 (70.0%)		18	11 (61.1%)	7 (38.9%)
Middle	146	63 (43.2%)	83 (56.8%)		152	82 (53.9%)	70 (46.1%)
Lower	60	37 (61.7%)	23 (38.3%)		47	28 (59.6%)	19 (40.4%)
Tumor size (cm)				0.926				0.985
≤4‡	137	65 (47.4%)	72 (52.6%)		140	78 (55.7%)	62 (44.3%)
>4	79	38 (48.1%)	41 (51.9%)		77	43 (55.8%)	34 (44.2%)
Differentiation				0.103				0.092
Well	28	14 (50.0%)	14 (50.0%)		39	27 (69.2%)	12 (30.8%)
Moderate	148	76 (51.4%)	72 (48.6%)		140	77 (55.0%)	63 (45.0%)
Poor	40	13 (32.5%)	27 (67.5%)		38	17 (44.7%)	21 (55.3%)
pT classification				0.033				0.268
T1	13	9 (69.2%)	4 (30.8%)		7	6 (85.7%)	1 (14.3%)
T2	55	32 (58.2%)	23 (41.8%)		49	27 (55.1%)	22 (44.9%)
T3	148	62 (41.9%)	86 (58.1%)		161	88 (54.7%)	73 (45.3%)
pN classification				0.002				0.002
N0	120	61 (50.8%)	59 (49.2%)		113	76 (67.3%)	37 (32.7%)
N1	48	30 (62.5%)	18 (37.5%)		63	29 (46.0%)	34 (54.0%)
N2	37	10 (27.0%)	27 (73.0%)		34	15 (44.1%)	19 (55.9%)
N3	11	2 (18.2%)	9 (81.8%)		7	1 (14.3%)	6 (85.7%)
Stage				0.021				0.001
I	13	8 (61.5%)	5 (38.5%)		12	11 (91.7%)	1 (8.3%)
II	124	67 (54.0%)	57 (46.0%)		114	71 (62.3%)	43 (37.7%)
III	79	28 (35.4%)	51 (64.6%)		91	39 (42.9%)	52 (57.1%)

*Chi-square test;

^†Median age;

^‡Median size.