We aim to evaluate safety and feasibility of a thulium laser system in performing endoscopic submucosal dissection of gastric neoplasia.

Instead of endoscopic knives, a thin, flexible fiber is inserted through the working channel of the endoscope. Acetic acid (1.5%) and indigo carmine dye are sprayed onto the lesion to clarify the margin. Markings are made 10 mm outside the tumor margin using a laser fiber with a power setting at 30 W. After marking, a mixture of sodium hyaluronate with indigo carmine and epinephrine (1:25000) is injected into the submucosa outside the marking dots. A circumferential mucosal incision and submucosal dissection are performed by a thulium laser fiber with a power setting at 30 to 40 W. Activation of the laser beam is controlled by stepping on a foot pedal. Hemostasis during procedure is also attempted using the thulium laser. When hemostasis is not achieved properly, additional use of hemostatic forceps or a hemoclip will be considered.

Inclusion Criteria:

• biopsy-proven gastric epithelial neoplasia

Exclusion Criteria:

• a.differentiated adenocarcinoma, ulcer(+), more than 3cm b.differentiated adenocarcinoma, submucosal invasion(+), more than 3cm c.undifferentiated adenocarcinoma, more than 2cm

All patients are diagnosed with gastric epithelial neoplasia in a private clinic and referred to our hospital for endoscopic resection.