Clinical features, diagnosis, and treatment of colorectal cap polyposis

Figure 1 Typical endoscopic features of cap polyposis. All polyps had a characteristic “cap-like” appearance with white fibrinous exudate covering the surface.

Figure 2 Characteristic histopathological features of cap polyposis. A-C: Hematoxylin and eosin staining. Erosive mucosal surface covered by thick inflammatory granulation tissue (pseudomembrane) with architectural disarray and prominent cystic dilation of crypts (A). Dense mixed inflammatory cell infiltration within the lamina propria (B). Elongated, dilated, and distorted crypts with a preserved glandular architecture and an absence of significant cytological atypia (C); D: Periodic acid-Schiff reaction. Periodic acid-Schiff reaction highlighting the fibrin-rich pseudomembrane overlying the mucosa.

Figure 3 Endoscopy revealed multiple polyps in the lower rectum of the patient, all of which were covered with fibrinopurulent exudate. Dozens of cap polyps were resected by transanal surgery. No recurrence of cap polyps was observed on follow-up colonoscopy.

Figure 4 Histopathological changes in patient 4 with hypoalbuminemia. A-C: Hematoxylin and eosin staining. Crypts markedly dilated by abundant intraluminal mucus retention (A). Goblet cell hyperplasia with prominent intracellular mucin vacuoles (B). Extracellular mucus pooling within crypt lumens and superficial lamina propria (star; C); D: Periodic acid-Schiff reaction. Periodic acid-Schiff reaction confirming glycoprotein-rich mucus accumulation (intracellular and extracellular).

Figure 5 Suggested management flow for cap polyposis patients. EMR: Endoscopic mucosal resection; ESD: Endoscopic submucosal dissection.