case_images: PMC11208811_01
case_images: Diagnostic features of retrorectal cyst. (a) Colonoscopy reveals a hemispheric protrusion on the posterior wall of the rectum. (b) EUS showed a clearly defined hypoechoic mass measuring 25 x 13 mm.
case_images: CRIGM2024-5538439.001.jpg
case_images: PMC11208811_01_CRIGM2024-5538439.001.jpg
case_images: fig1
case_images: On the endoscopy, a hemispheric bulge, 2 cm in diameter and covered with intact mucosa, was observed on the posterior rectal wall at 11 cm from the anal verge (Figure 1(a)). Due to contraindications for magnetic resonance imaging (MRI), endoscopic ultrasonography (EUS) was conducted, displaying a 25 x 13 mm oval-shaped tumor with a hypoechoic inhomogeneous content with a well-defined margin, close fitting to the posterior wall of the rectum, connected with its muscle layer (Figure 1(b)).
case_images: Retrorectal extraluminal endoscopic resection of tailgut cyst. (a) After dissecting the mucosa, submucosa, and circular muscle layer of the rectum, the cyst is visible. (b) Fibers of longitudinal muscle layer, attached to the upper part of the cyst capsule. (c) Rectal fascia, covering the cyst on the right side. (d) The cyst is partly separated from the surrounding tissues. (e) Dissection of dense band between loose connective tissues. (f) Tumor bed (on the left) after removal. (g) The mucosal incision was closed with 4 endoclips. (h) Macroscopic appearance of the lesion.
case_images: CRIGM2024-5538439.002.jpg
case_images: PMC11208811_01_CRIGM2024-5538439.002.jpg
case_images: fig2
case_images: Subsequently, a short submucosal tunnel was created, and thin, distended fibers of the internal muscular layer were visualized and dissected (Figure 2(a)). The tumor itself lay beneath, and its capsule was attached to the longitudinal muscular fibers (Figure 2(b)). The lesion was separated from the muscular layer, rectal fascia, and then from the fat and connective tissue of retrorectal space in a step-by-step manner (Figures 2(c) and 2(d)). Loose connective and adipose tissues were divided with denser bridges, connected to the cyst capsule (Figure 2(e)). The tumor bed was revised (Figure 2(f)). Blood vessels had been coagulated with a coagrasper. 4 endoscopic clips were applied for the ultimate closure of the mucosa (Figure 2(g)). Macroscopically, the removed tumor looked like a round cystic neoplasm with a diameter of 2.5 cm (Figure 2(h)); on the cross section, the cavity was filled with a thick fluid of light brown color.
case_images: Microphotograph of tailgut cyst. (a) Multilocular structure, lined with transitional epithelium (blue arrow), serous epithelium (black arrow), and intestinal-type tall columnar mucinous epithelium with basally located nuclei (green arrow). The bundles of smooth muscle are visible within the stroma (H&E; x20). (b) The cystic wall (on the left) and mucous content (on the right) (H&E; x40).
case_images: CRIGM2024-5538439.003.jpg
case_images: PMC11208811_01_CRIGM2024-5538439.003.jpg
case_images: fig3
case_images: Histology showed cystic hamartoma (tailgut cyst) (Figures 3(a) and 3(b)).