The normal colonic wall is visualized as a nine-layered structure by EUS (HFUP). The first three echo layers, mucosa; the fourth thin, hypoechoic layer, muscularis mucosa; the fifth high-echo layer, submucosa; the sixth low-echo layer, inner circular muscle; the seventh thin, high-echo layer, intermuscularis propria layer; the eighth low-echo layer, outer longitudinal muscle; and the ninth high-echo layer, subserosa and serosa
5.4 EUS Findings of Colorectal Carcinoma at Each Invasion Depth
![../images/461529_1_En_5_Chapter/461529_1_En_5_Fig2_HTML.jpg](https://i0.wp.com/abdominalkey.com/wp-content/uploads/2020/08/461529_1_En_5_Fig2_HTML.jpg?w=960)
EUS images of the colorectal cancers at each invasion depth. (a) Adenoma and Tis were visualized as a hypoechoic mass localized within the first three layers, while the fourth thin hypoechoic layer, muscularis mucosae (arrow), was intact. (b, c) T1a cancers, focal extension of the cancer to the fifth layer (arrow). (d) T1b (SM2) cancer, moderate extension of the cancer to the fifth layer. (e) T1b (SM3) cancer, massive extension to the fifth layer with the sixth layer intact. (f) MP1 cancer, focal extension of the cancer to the sixth layer (arrow)
5.5 Accuracy of the Diagnosis of Tumor Invasion
![../images/461529_1_En_5_Chapter/461529_1_En_5_Fig3_HTML.png](https://i0.wp.com/abdominalkey.com/wp-content/uploads/2020/08/461529_1_En_5_Fig3_HTML.png?w=960)
The accuracy rate of the invasion depth diagnosis (274 lesions). (a) The overall accuracy rate was 77.3% (211/274) for the choice of therapy. The accuracy rate was 69.2% (108/156) in Tis-T1a carcinomas and 87.3% (103/118) in T1b carcinomas; the values were significantly higher in T1b carcinomas than in Tis-T1a carcinomas (p < 0.001; chi-square test). (b) The accuracy rate was significantly higher for F&D-type carcinomas (82.8%; 125/151) than for polypoid-type ones (69.9%; 86/123) (p < 0.001) and significantly higher for T1b carcinomas than for Tis-T1a carcinomas in both macroscopic types (p < 0.001, respectively)
5.6 Case Presentation
![../images/461529_1_En_5_Chapter/461529_1_En_5_Fig4_HTML.png](https://i0.wp.com/abdominalkey.com/wp-content/uploads/2020/08/461529_1_En_5_Fig4_HTML.png?w=960)
A flat elevated (IIa)-type T1b cancer 15 mm in size in the rectum. (a) The colonoscopic findings with indigo carmine dye spray showed a flat elevated lesion with central smooth protrusion. (b, c) EUS showed a hypoechoic mass with moderate invasion of the submucosal layer. (d) Histopathological specimens showed this lesion to be a IIa-type T1b (SM2) cancer with 1350 μm of submucosal invasion
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