PMC9035920_01
Endoscopic findings of the lesion. a The lesion shows a SET. A bridging hold was observed on the smooth surface of the lesion under white light; the lesion has a solid appearance. b Image after indigo carmine spraying. No ulcer or erosion is observed on the lesion surface. c No irregular vessels are observed on the lesion surface in narrow-band imaging. d EUS indicated that this SET might be located at the second or third layers but did not provide additional information due to poor endoscopic manipulation and deep echo attenuation.
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F1
He underwent endoscopy in our hospital, which showed a 10 mm SET, without ulceration or cushion sign (Fig. 1). Furthermore, EUS via the water-filling method using an ultrasound probe demonstrated that this lesion might be derived from the second or third layers; however, it did not provide additional information for the differential diagnosis of SET due to the insufficient manipulation of the scope (Fig. 1d).
Endoscopic images during ESD. a A loop was formed in the transverse colon, and the scope manipulation was poor. b A single-use splinting tube was placed before the ESD procedure. c Poor visualization of the cutting area makes colorectal ESD difficult. d Mild fibrosis is identified during the dissection of the submucosa. e The edge of the exfoliated mucosa was attached with the spring S-O clip, which makes cutting submucosal area more visible. f Immediately after ESD, the resected specimen is measured and is found to be 25 x 20 mm.
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F2
Ltd, Tokyo, Japan) for stable endoscopic manipulation (Fig. 2a, b). Because fibrosis was observed in the submucosa (Fig. 2c, d), the spring S-O clip traction method (TC1H05, Zeon Medical Tokyo, Tokyo, Japan) facilitated submucosal dissection (Fig. 2e). Finally, en bloc resection was achieved in 44 min without any adverse events (Fig. 2f).
Histological findings of the resected specimens. a The lesion is 8 x 7 mm. It is located in the submucosa, and the surface is covered with non-neoplastic mucosa. b Atypical cells with round-to-oval nuclei and acidophilic vesicles are observed (HE staining. x400 magnification). c Immunohistochemistry reveals strong expression of S-100 protein in the lesion. d Low expression of Ki-67 labeling (x200 magnification).
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F3
Atypical cells with round-to-oval nuclei and acidophilic vesicles were observed on HE staining (Fig. 3a, b). Moreover, immunohistochemical staining for S-100 protein was strongly positive, and the Ki-67 labeling index was 5% (Fig. 3c, d).