Gastric cancer is one of the main causes of cancer death in China. Most of these patients have poor prognosis because of late presentation and diagnosis. The best tactics for dealing with gastric cancer is prevention, early detection and early treatment. It is generally believed that gastric cancer is a multi-step progression from chronic gastritis to gastric atrophy, intestinal metaplasia, dysplasia and cancer. Early gastric cancer is defined as a cancer confined to the mucosa or submucosa regardless of lymph node metastasis . If gastric cancer can be detected in early stage, the prognosis for gastric cancer is excellent, the survival rate is greater than 90% in 5 years, and curative endoscopic resection may be possible in some cases with early gastric cancers and precancerous gastric lesions, without the need for surgery. Therefore, it is necessary to mass screen for symptomatic groups in high-incidence areas, and endoscopy has been considered as one of the most useful tool for detecting early gastric cancer. However, at present, only about 4-10% of patients with gastric cancer are diagnosed as early cancer in China, and the missed diagnosis of gastric cancer on endoscopy is a common occurrence. It is reported that the false-negative rates are high up to 5-19% [11, 12]. There may be two reasons for this situation. One reason is that the symptoms of early gastric cancer are not specific to distinguish from those of gastritis and benign peptic ulcer disease. In our group, about 90% of patients with early gastric carcinoma have heartburn, abdominal pain and discomfort in the upper abdomen. The other reason is that some of the lesions are so subtle that they are overlooked by inexperienced endoscopist. Without being aware of early gastric cancer, they pay much attention to the detection of gross lesions, rather than tiny changes in color, vascularity or texture, which are distinctive characteristics of early gastric cancer. There has been great advancement about the technology of endoscopic imaging in recent years, and these new technologies have improved the sensitivity in identifying early gastric cancer.
Magnifying endoscope (GIF-Q240Z) used in our study can provide magnified images up to x80. This new magnifying endoscope can detect minute changes of gastric mucosal surface, such as the color of lesions (same color as surrounding tissues, red or pale), the surface of lesions (flat, elevated or depressed), the presence of granules or nodules, with or without ulcer and fold change. Irregular and destruction of the minute surface pattern and color change of mucosal surface were all considered as characteristics of precancerous gastric lesion or early gastric cancer [13–15].
Dye spray chromoendoscopy can enhance the recognition of minute structural alteration caused by neoplastic changes, which is difficult to be perceived by conventional endoscopy. Magnifying chromoendoscopy is also useful in observing the surface mucosal pattern and capillary structure. By analyzing the surface structure pattern, histological changes of carcinoma, dysplasia, adenoma and hyperplasia might be suspected. Since histopathological examination of biopsy material is very important for the final diagnosis, accurate biopsy contributes to acquire the correct diagnosis of the lesion. Magnifying chromoendoscopy can improve the diagnosis of early gastric cancer and precancerous lesions in the stomach by facilitating the identification and biopsy of abnormal areas. It is difficult in some cases to identify the margins of the lesions by conventional endoscopy, especially those of superficial or flat-type lesions. Magnifying chromoendoscopy has an advantage in coping with this difficulty [13, 16].
Narrow-band imaging (NBI) is a new kind of endoscopic technology designed to enhance the contrast of the mucous membrane without staining. NBI uses special narrow-band filters which filter broad-band spectrum to leave a narrow-band spectrum for the diagnosis of digestive tract disease [17–19]. NBI endoscopy significantly improves diagnostic accuracy in two ways. First, because the shorter wavelength light left by the special narrow-band filter can not penetrate deeply into the mucosa, NBI improves visibility of mucosal pit pattern. Second, since the specific wavelength 415 nm left by special narrow-band filter corresponds to the peak absorption spectrum for hemoglobin , magnifying the image with NBI can give important information about microvascular pattern .
In our study, we find that the image quality of magnifying NBI is superior not only to magnifying conventional endoscopy in respect of morphology, pit pattern and blood capillary form of abnormal areas, but also to magnifying chromoendoscopy concerning blood capillary form. However, in our study, the image quality was scored during the examination, and the scoring system itself has subjective nature, so it would be better to score the image quality in a blinded fashion by more investigators. We also find that the diagnotic accuracy of early gastric cancer and precancerous gastric lesions by magnifying NBI is significantly higher than that of conventional endoscopy. Moreover, NBI has all the functions that conventional endoscopy has, and the NBI and conventional endoscopy pattern can be easily switched just by pushing one button [22, 23].
Both NBI and chromoendoscopy can show the enhanced mucosal pattern and the microvascular structure of the mucosa by the amplificatory function, and mucosal pattern and microvascular structure have been regarded as distinctive characteristics of early gastric cancer and precancerous gastric lesions.
It has been known that angiogenesis is an important factor in gastrointestinal carcinogenesis , suggesting that the vascular pattern of gastric cancer and precancerous gastric lesion is differ from that of normal mucosa . Therefore, observation of vascular pattern contributes to diagnosis of such lesions . Nakayoshi  et al observed the microvascular networks of 165 patients with early gastric carcinoma with magnifying NBI, and found that 66.1% of differentiated adenocarcinoma had fine microvascular networks, and 85.7% of undifferentiated adenocarcinoma had corkscrew microvascular networks. Liu  et al also drawn the conclusion that vascular architecture was helpful in the identification of early gastric cancer. They studied the microvascular architecture with confocal endomicroscopy, and demonstrated that differentiated gastric cancerous mucosa showed hypervascularity and various caliber microvessels with irregular shapes, and undifferentiated gastric cancer showed hypovascularity and irregular short branched vessels. In our study, we found abnormal capillary patterns in 109 cases including disappearance of the normal mucosa capillary network, tortuous microvessels with irregular length and irregular arrangement, and variation in the caliber of vessels or even dilated microvessels with tortile tips. However, at present, as a new technology, there is no unified standard for diagnosis of early gastric carcinoma by using microvascular architecture.
Many studies have shown that gastric mucosa patterns of gastric cancer and precancerous gastric lesions are characteristic. Tanaka et al classified pit patterns of gastric mucosa into five types, and pointed out that differentiated tubular adenocarcinomas mainly showed the type IV, and poorly differentiated tubular adenocarcinomas mainly showed type V . Yoshida et al distinguished gastric cancer and precancerous gastric lesions from controls by analyzing the surface structure pattern . In our study, V1 and VI type of gastric pit pattern are the most common mucosa pattern of early gastric cancer and precancerous lesions. Therefore determination of pit pattern as well as microvascular architecture is very important for detecting early gastric cancer and precancerous lesion .