When performing screening endoscopy, small focal gastric lesions are frequently encountered. Novel techniques in endoscopy, such as magnifying endoscopy (ME) with narrow-band imaging (NBI) and chromoendoscopy with acetic acid-indigocarmine mixture (AIM), are developing to enhance images of gastrointestinal tumor. Furthermore, observation of the microstructures of gastric mucosa by ME, including microvascular pattern and microsurface pattern, has been proposed in the recognition of early gastric cancer (EGC).

This study is based on the hypothesis as follow:

1. The microvascular structure could be clearly observed with magnifying endoscopy enhanced by narrow-band imaging (ME-NBI).
2. The microsurface architecture could be clearly observed with magnifying endoscopy enhanced by acetic acid-indigocarmine mixture (ME-AIM).
3. Enhanced ME (combining ME-NBI and ME-AIM), as compared to white-light endoscopy (WLE), has higher sensitivity and specificity for the differential diagnosing small focal gastric lesions.

Patients who received surveillance endoscopy for EGC using a zoom endoscope were eligible for inclusion. WLE without magnification was performed first in eligible patients. Based on an assessment of the shape (such as flat, depressed or elevated) and color (pale or reddened), small focal gastric lesions were identified and included for evaluation by experienced endoscopists. When such a lesion was detected during non-magnifying observation with WLE, the mode was then changed to ME-NBI for observation of microvascular pattern and ME-AIM for observation of microsurface pattern subsequently. All endoscopic images of the whole procedure were recorded in digital filing system for later evaluation. To avoid possible selection bias and to maintain the quality of the study, all images of each endoscopic modality (including WLE, ME-NBI, ME-AIM), which were arranged randomly on one slide and displayed independently of the images of other endoscopic modality, were evaluated by 4 skilled endoscopists, who were not access to the clinical and pathological data. The general consensus was established for an assessment of each lesion. Two forceps biopsy specimens were taken from each lesion and pathological diagnosis were used as the criterion standard for cancer diagnosis.

Inclusion Criteria:

• Patients, in which small focal gastric lesions were identified with conventional WLE, were enrolled in this study. Before being enrolled, all patients provided written informed consent.

Exclusion Criteria:

• Patients who cannot undergo gastroscopies due to unsuitable conditions
• Referred patients with a history of having being diagnosed as gastric cancer
• Patients with a personal history of gastric surgery
• Patients who cannot provide informed consent
• Patients with advanced gastric cancer

Patients who received surveillance endoscopy for EGC using a zoom endoscope were eligible for inclusion.