Diagnosis of colorectal tumor invasion by endoscopic miniature probe ultrasonography.

We evaluated the diagnostic efficacy of high-frequency (20 MHz) ultrasound probe (HFUP) for the staging of invasive depth of colorectal tumors. The subjects were 27 patients with colorectal tumorous lesions who were treated by endoscopic or surgical operation (11 patients with lesions remaining in the mucosa, 13 patients with submucosal cancer, and 3 patients with cancer invading the muscularis propria or deeper layers). Considering the previous reports that endoscopic mucosal resection (EMR) is indicated in cases of tumors remaining in the mucosa or cancer slightly invading the submucosal layer, we divided the submucosal layer vertically into three equal areas (most superficial, middle and deepest areas which were referred to as sm1, sm2 and sm3, respectively). The depth of tumor invasion in histological specimens was compared to the depth of tumor invasion as assessed preoperatively using the HFUP. The HFUP-based diagnosis was identical to the histological diagnosis in 86.4% of all cases, when the depth of tumor invasion was rated on a three-point scale: (i) m-sm1, (ii) sm2-sm3 or (iii) mp or deeper. These results indicate that the HFUP is very useful in selecting a therapeutic method for colorectal tumors.