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Background: A pink color change occasionally found by us under magnifying endoscopy with narrow-band imaging (ME-NBI) may be a special feature of early gastric cancer (EGC), and was designated the “pink pattern”. The purposes of this study were to determine the relationship between the pink pattern and the cytopathological changes in gastric cancer cells and whether the pink pattern is useful for the diagnosis of EGC.Methods: The color features of ME-NBI images and pathological images of cancerous gastric mucosal surfaces were extracted and quantified. The cosine similarity was calculated to evaluate the correlation between the pink pattern and the nucleus-to-cytoplasm ratio of cancerous epithelial cells. Two diagnostic tests were performed by 12 endoscopists using stored ME-NBI images of 185 gastric lesions to investigate the diagnostic efficacy of the pink pattern for EGC. The diagnostic values, such as the area under the curve (AUC), the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), of test 1 and test 2 were compared.Results: The cosine similarity between the color values of ME-NBI images and pathological images of 20 lesions was at least 0.744. The median AUC, accuracy, sensitivity, specificity, PPV, and NPV of test 2 were significantly better than those of test 1 for all endoscopists and for the junior and experienced groups.Conclusions: The pink pattern observed in ME-NBI images correlated strongly with the change in the nucleus-to-cytoplasm ratio of gastric epithelial cells, and could be considered a useful marker for the diagnosis of differentiated EGC.

Background A pink color change found occasionally by us under the magnifying endoscopy with narrow-band imaging (ME-NBI) may be a special feature of early gastric cancer (EGC), and it was named as “pink pattern”. The purposes of this study were to reveal the relationship between the “pink pattern” and the cytopathological changes of gastric cancer cells, and explore whether the pink pattern was useful for the diagnosis of EGC. Methods The color features of ME-NBI images and pathological images on gastric cancerous mucosal surface were extracted and quantized, and then the cosine similarity was calculated to evaluate the correlation between the pink pattern and the nucleus-to-plasm ratio of cancerous epithelial cells. Two diagnostic tests were performed by 12 endoscopists using stored ME-NBI images of 185 gastric lesions to investigate the diagnostic efficiency of “pink pattern” for EGC. The diagnostic values such as area under curve (AUC), accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) between test 1 and test 2 were compared. Results The cosine similarity in 20 lesions between the color values of ME-NBI images and pathological images was at least 0.744. The median AUC, accuracy, sensitivity, specificity, PPV and NPV of test 2 were significantly improved compared with that of test 1 in all endoscopists, junior and experienced groups. Conclusions The “pink pattern” visualized in ME-NBI images is highly correlated with the nucleus-to-plasma ratio change of gastric epithelial cells, and it can be considered as a useful marker for the diagnosis of the differentiated EGC.