Table 1 Identification of Elastic Lamina (EL) and Elastic Lamina Invasion (ELI)

a. EL and Tumor Location

EL

Tumor Location

C

A

T

D

S

Rs

Ra

p-value

Total

Identified

29

87

62

32

157

88

65

0.014*

520

(91.4)

Unidentified

(%)

3

(9.4)

11

(11.2)

6

(8.8)

4

(11.1)

9

(5.4)

5

(5.4)

11

(14.5)

49

(8.6)

C cecum, A ascending colon, T transverse colon, D descending colon, S sigmoid colon, Rs recto-sigmoid colon, Ra intraperitoneal rectum above the peritoneal reflection; *A/D/Ra vs. C/T/S/Rs: Chi-square test showed a significant correlation between tumor location and EL

b. EL and Tumor Size

EL

Tumor size

 < 3 cm

3-5 cm

 ≥ 5 cm

Unknown

p-value

Total

Identified

32

192

293

3

 < 0.0001^*

520

(91.4)

Unidentified

(%)

17

(34.7)

27

(12.3)

5

(1.7)

0

49

(8.6)

^*Chi-square test showed a significant correlation between tumor size and EL

c. EL and Circumferential Distribution at A, D, and Ra

EL

Circumferential Distribution

Posterior

Anterior

Lateral

Whole

circumference

Unknown

p-value

Total

Identified

20

61

20

82

1

 < 0.0001^*

184

(87.6)

Unidentified

(%)

16

(44.4)

4

(6.2)

4

(16.7)

2

(2.4)

0

26

(12.4)

A ascending colon, D descending colon, Ra intraperitoneal rectum above the peritoneal reflection

^*Chi-square test showed a significant correlation between circumferential distribution and EL

d. ELI and cT

cT

pT3, n = 544, (%)

pT4a, n = 25, (%)

p-value

Total

pT3a [ELI −]

pT3u [EL −]

pT3b [ELI +]

[ELI +]

cT3

cT4a

128 (60.1)

113 (31.7)

44 (20.7)

5 (1.4)

38 (17.8)

216 (60.7)

3 (2.8)

22 (6.2)

 < 0.0001^*

213

356

Total

241

49

254

25

569

^*Chi-square test showed a significant correlation between cT and pT categories