PMC10235794_01
Endoscopic findings of traditional serrated adenoma (TSA) with superficially serrated adenomas (SuSA). (a) Colonoscopy shows a raised lesion with a two-tier raised appearance in the sigmoid colon, consisting of a tall pinecone structure and flattened elevation. Indigo carmine dye spray highlights the nodular surface. (b) The yellow box indicates the boundary between the TSA and SuSA components, which is magnified in Figure 1c. The red box indicates a typical part of the SuSA component, which is magnified in Figure 1d. (c) High-power view showing the boundary between the TSA and SuSA components (the yellow box in Figure 1b). The TSA component appears reddish on white-light imaging. (d) High-power view of the SuSA component (the red box in Figure 1b). The SuSA component appears white, with a smooth surface on white-light imaging.
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Colonoscopy showed a raised lesion, approximately 25 mm in size, with a two-tier raised appearance in the sigmoid colon, consisting of a tall pinecone-like structure and a flattened elevation (Figure 1a). The pinecone-like structure appeared reddish (Figure 1c), and the flattened area was white to the same color as the surrounding background mucosa (Figure 1d) on white-light imaging.
Narrow-band imaging (NBI) and crystal violet staining revealing features of traditional serrated adenoma (TSA) and superficially serrated adenoma (SuSA). (a) NBI magnification reveals conspicuous blood vessels in the pinecone structure of the TSA. (b) The vessels are unclear on magnifying NBI in the flat areas of the SuSA. (c) Crystal violet staining shows that the pinecone structure of the TSA has a type IVH pit pattern. (d) Crystal violet staining shows that the flat area of the SuSA has a stellate to slightly elongated type IIIH pit. Abbreviation: NBI, narrow-band imaging.
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Magnifying narrow-band imaging (NBI) revealed conspicuous blood vessels in the pinecone-like structure (Figure 2a) and slightly dilated reticular vessels in the flattened areas (Figure 2b). Crystal violet staining showed that the pinecone-like structure had an IVH-type pit pattern, diagnosed based on Kudo's classification and other pit pattern classification systems (Figure 2c). The flattened area showed a stellate to slightly elongated IIIH-type pit pattern (Figure 2d).
Histological features of traditional serrated adenoma (TSA) with superficially serrated adenomas (SuSA). (a) Low-power images of the polyps showing the proliferation of adenomatous glands and superficial serration using H&E staining. (b) High-power view of the TSA component (the red box in Figure 3a). The TSA component shows classical histological features, such as villous architecture and ectopic crypt formation. (c) High-power view showing the boundary between TSA and SuSA components. A clear demarcation line (blue broken line) can be drawn between the TSA and SuSA (the blue box in Figure 3a). (d) High-power view showing the SuSA (the yellow box in Figure 3a). The SuSA component consists of straight serrated adenomatous glands exhibiting serration confined to the superficial layer. Serration is confined to the surface epithelium and crypt orifice. Histopathological examination reveals a dense proliferation of glandular ducts with pseudostratified nuclei and a serrated surface around the TSA. Slit-like serrations, penicillate nuclei, and ectopic crypt foci are observed in the pinecone structure. These are specific features of the SuSA. Abbreviation: HE, hematoxylin and eosin.
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Immunohistochemical staining of superficially serrated adenoma (SuSA). (a) CK20 is expressed in the upper layer of the SuSA. (b) Ki-67 expression is distributed in the middle to lower layers of the SuSA. (c) C-MYC expression is distributed in the middle to lower layers of the SuSA. (d) A SuSA shows moderate nuclear beta-catenin staining in addition to membranous staining.
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Ki-67 and MYC expressions were distributed in the basal and middle layers of the flattened structure (Figure 4b,c). Additionally, beta-catenin, suggesting the activation of the Wnt pathway, was found in some nuclei (Figure 4d).