Diagnosis of small flat early gastric cancer by flexible spectral imaging color enhancement.

Current conventional endoscopy often misses flat early gastric cancers (0-IIb) because they are sometimes invisible. We experienced a case of small flat early gastric cancer that had been missed by normal-caliber conventional endoscopy. By small-caliber endoscope, conventional endoscopy showed a subtle reddish change of gastric mucosa, but the image with flexible spectral imaging color enhancement clearly showed a flat reddish lesion with 10 mm diameter, distinct from the surrounding mucosa. Flat early gastric cancer was suspected even though the lesion was not clearly described by conventional endoscopy. Histological examination of biopsy specimen revealed atypical glands. Endoscopic submucosal dissection of the lesion was performed. Pathological examination of the resected specimen confirmed well-differentiated adenocarcinoma localized in the mucosal layer without any depression or protrusion compared with the surrounding mucosa, consistent with the endoscopic finding. The small flat early gastric cancer became clearly visible with the new endoscopic technology.