Clinical application of oral contrast-enhanced ultrasound in evaluating the preoperative T staging of gastric cancer

Table 1 Pathological and ultrasonic T staging criteria

T stages	Pathological definition	Ref. ultrasonic imaging
T1a	The tumor invades the lamina propria or the mucosal muscularis layer	Layer 1 (superficial mucosal layer) continuity interrupted, Layer 2 (deep mucosal layer) low-echo thickening, Layer 3 (submucosa) remains continuous
T1b	The tumor invades the submucosa	Layer 3 (submucosa) high-echo continuity interrupted, muscularis propria layer and serosa layer is intact
T2	The tumor invades the muscularis propria	Layer 4 (muscularis propria) low-echo invasion, with the outer layer retaining a smooth echo boundary
T3	The tumor penetrates the subserosal connective tissue but does not invade the visceral peritoneum	Each layer structure completely disappears, but the outermost layer retains a smooth high-echo band (serosal layer)
T4a	The tumor invades the serosal membrane (visceral peritoneum) but not the adjacent structures/organs	Each layer structure completely disappears, and the high-echo band (serosal layer) disappears, or there is a clearly visible serosal layer high-echo line breakthrough with a burr sign or crab foot sign
T4b	Tumors invade the adjacent structures/organs	The whole layer is involved, and the echo boundary between the adjacent organ structure (aorta, pancreas, liver, etc.) disappears, and it adheres with the adjacent organs without relative movement