PMC5968291_01
Endoscopic features of the lesion at the caecum. a Colonoscopy detected a 20 x 16 mm white, flat, elevated lesion with a reddish nodule in the center of the mass. b Chromoendoscopy of crystal violet solutions showed mucus covering a wide-open pit (square yellow box). c Crystal violet solutions revealed mucus covering a dendritic structure (square blue box). d The central reddish nodule demonstrated an irregular glandular structure (square red box).
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F1
Colonoscopy showed a 20 x 16 mm white, flat, elevated lesion with a reddish nodule in the center of the mass (Fig. 1a) located at the caecum. Chromoendoscopy with crystal violet solutions revealed mucus covering a wide-open pit (Fig. 1b) and a large dendritic structure (Fig. 1c). At the central area, the reddish nodule displayed an irregular glandular structure (Fig. 1d).
Histological features of the resected tumor. a Three regions, including area A (square yellow box), B (square blue box), and C (square red box), were formed in the tumor. b The tumor was composed of 3 areas (areas A, B, and C) histologically. c Area A (endoscopically, a wide-open pit was detected) revealed crypt dilatation, irregular branching, and abnormal histological architecture at the crypt base, suggesting SSA/P. d Area C (endoscopically, an irregular glandular structure was detected) demonstrated cytological atypia and a complex architecture with tubular or cribriform pattern, indicating carcinoma (differentiated-type adenocarcinoma) that invaded the submucosa (depth of submucosal invasion, 1,250 mum). e Area B (endoscopically, a large dendritic structure was detected) showed more irregular branching and less abnormal architecture at the crypt base than area A, suggesting high-grade SSA/P. SSA/P, sessile serrated adenoma/polyp.
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F2
A, B, and C) (Fig. 2a, b). A had crypt dilatation, irregular branching, and abnormal histological architecture at the crypt base (Fig. 2c). Area A was diagnosed as SSA/P. Area B showed more irregular branching and less abnormal architecture at the crypt base than area A (Fig. 2e). Although the cellular atypia of area B was not different from that of area A, the structural atypia of area B was greater than that of area A. Area C demonstrated cytological atypia and a complex architecture with tubular or cribriform findings (Fig. 2d).
Immunohistochemical findings of the tumor. a Expression of MUC2 was commonly seen in areas A, B, and C. b MUC5AC was commonly expressed in areas A, B, and C. c Expression of MUC6 was found in area A. d TP53 overexpression was seen in areas B and C. e MLH1 expression was found in areas A, B, and C. Note that MLH1 was expressed in areas B and C.
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F3
TP53 was seen in area C. The immunohistochemical findings are shown in Figure 3.