Signet ring cell carcinoma hidden beneath large pedunculated colorectal polyp: A case report

BACKGROUND: Large pedunculated colorectal polyps are not frequent among colonic polyps. We present a clinical case of a large pedunculated colorectal polyp with signet ring cell cancer infiltrating the submucosa and lymph node invasion in a patient who ultimately underwent additional surgery. Clinicians should attach importance to pedunculated colorectal polyps and choose the most appropriate therapy. CASE SUMMARY: A 52-year-old female farmer underwent routine screening colonoscopy and denied constipation, diarrhea, hematochezia, or other gastrointestinal symptoms. Her past medical history and general biochemical examination results were unremarkable. During the colonoscopy, a 25-mm pedunculated polyp in the sigmoid colon was identified. The superficial epithelium was macroscopically congestive, rough, and granular, showing characteristic features of adenoma. We first ligated the root of the pedunculated polyp using nylon loops as well as a titanium clip. Histopathological examination revealed high-grade intraepithelial neoplasia of the tumor surface and a negative margin with signet ring cell adenocarcinoma infiltrating the submucosal layer. The deepest infiltration was approximately 0.9 cm from the tumor surface and 0.55 cm from the stratum basale. We performed radical resection of the left colon with lymph node dissection after two weeks. The lesion was completely resected, and pathological assessment revealed signet ring cell adenocarcinoma infiltrating the submucosal layer as well as lymph node invasion (stage PT1N1M0 and grade IIIA in pathological grading, NRAS-, BRAF V600E-, KRAS-). CONCLUSION: This case highlights the importance of paying attention to the malignancy of large pedunculated polyps. Polyps or adenomas removed via endoscopy must be evaluated histologically. Even if adenomas may be fragile, endoscopy doctors should still remove polyps as completely as possible and choose perpendicular sections through the stalk and base to fix by formaldehyde solution.