Small ultrasonic probes for determination of the depth of superficial esophageal cancer

Background: In esophageal cancer it is important to distinguish between mucosal cancer and cancer invading the submucosa to determine the feasibility of endoscopic mucosal resection. Methods: Endoscopic ultrasonography using a small probe 2.6 mm in diameter at 15 or 20 MHz frequency was employed to determine the depth of superficial esophageal cancer invasion in 54 patients. Group 1 consisted of 17 cases treated by endoscopic mucosal resection on the basis of ultrasonographic findings. Group II included 37 patients treated by conventional surgery. The resected specimens were compared with ultrasonographic findings. Results: The normal esophageal wall was depicted as having nine layers, the fourth hypoechoic layer (m4) on the high frequency image was confirmed to be the muscularis mucosa. Based on the ultrasound findings, cancer limited to the lamina propria was accurately determined in 84%. In the endoscopic mucosal resection cases, 15 were mucosal cancer whereas 2 cases had microscopic invasion of the submucosa. Conclusions: High-frequency ultrasound probes were sufficiently accurate for the determination of the depths of invasion of early esophageal cancer to guide the application of endoscopic resection of mucosal cancer.