PMC7551980_01
A: LST-NG existed in the transverse colon. The arrow indicates the outline of the tumor. B: NBI enlargement observation showed that the surface pattern and vessel pattern were not irregular, so the tumor was diagnosed as JNET2B.. C: The pit pattern was IIIL on indigocarmine staining. The arrow indicates the outline of the tumor.. D: The pit structure was irregular on crystal violet staining.. E: EUS depicted the tumor as a low-echoic lesion (arrow) centering on the mucosal layer, and the submucosal layer was preserved. The submucosal layer is partially unclear, suggesting tumor invasion (arrowhead).
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Colonoscopy for an anemia examination indicated laterally spreading tumor-nongranular (LST-NG) in the transverse colon (Fig. 1A). The size of the tumor was about 30 mm, and Narrow Band Imaging (NBI) enlargement observation showed that the surface pattern and vessel pattern were not irregular, so the tumor was diagnosed as JNET2B (Fig. 1B). Although most of the tumor showed an IIIL pit pattern, as observed by indigocarmine staining, the pit structure was irregular on crystal violet staining, so the tumor was diagnosed as Vi irregular according to the Kudo pit pattern classification (Fig. 1C, D). Endoscopic ultrasonography (EUS) depicted the tumor as a low-echoic lesion centering on the mucosal layer, and the submucosal layer was partially unclear, with tumor invasion suspected (Fig. 1E).
Enema revealed that the tumor was located in the liver curvature (arrow showed tumor outline).
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The tumor localization was not clear on computed tomography (CT), but an enema revealed it to be present in the transverse colon near the liver curvature (Fig. 2).
A: The tumor was 20 x 20 mm in size. The arrow indicates the outline of the tumor.. B: The tumor was mainly a well-differentiated adenocarcinoma, but vesicles in which polygonal tumor cells with poor nuclear atypia had proliferated solidly were observed mainly in the submucosal layer (area enclosed by a broken line).. C: The tumor cells were positive for synaptophysin. The arrow indicates synaptophysin-positive tumor cells.. D: Tumor cells were positive for CD56. The arrow indicates CD56-positive tumor cells.. E: Tumor cells were negative for Ki-67. The arrow indicates Ki-67-negative tumor cells.
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Pathologically, the tumor was 20 x 20 mm in size, and the muscular layer of the mucosa was ruptured, so the tumor had slightly invaded the submucosa (Fig. 3A, B). Therefore, the tumor was considered to be a low-grade highly differentiated-type tubular adenocarcinoma (Fig. 3B). In addition, solid vesicles of polygonal tumor cells with poor nuclear atypia proliferating invasively in the submucosa were observed (Fig. 3B). These cells were positive for synaptophysin and CD56 and negative for Ki-67 and were thus considered carcinoid tumors (NET G1) (Fig. 3C-E).