In practice, the classification is difficult to apply as many pedunculated polyps have short stalks that are destroyed during mechanical snaring or diathermy. Also, the cut off between the head/neck and neck/stalk is often arbitrary and subject to inter-observer variability.
- Level 0
- Carcinoma in situ or intramucosal carcinoma. Not invasive. (Note: neither term is in use in the UK)
- Level 1
- Carcinoma invading through muscularis mucosa into submucosa, but limited to the head of the polyp.
- Level 2
- Carcinoma invading the level of the neck of the adenoma.
- Level 3
- Carcinoma invading any part of the stalk.
- Level 4
- Carcinoma invading into the submucosa of the bowel wall below the stalk of the polyp, but above the muscularis propria.
- ↑ Haggitt RC, Glotzbach RE, Soffer EE, Wruble LD. Prognostic factors in colorectal carcinomas arising in adenomas: implications for lesions removed by endoscopic polypectomy. Gastroenterology. 1985 Aug; 89(2):328-36.
- ↑ Kikuchi R, Takano M, Takagi K, Fujimoto N, Nozaki R, Fujiyoshi T, Uchida Y. Management of early invasive colorectal cancer. Risk of recurrence and clinical guidelines. Diseases of the colon and rectum. 1995 Dec; 38(12):1286-95.