T1 CRC Index • Submucosal Depth Matrix
Select the polyp morphology and invasion depth recorded in the pathology report to visualize the lymph node metastatic risk profile.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Histological evaluation of T1 colorectal cancers (cancers invading the submucosa but not the muscularis propria)
To predict the risk of Lymph Node Metastasis (LNM)
To guide the decision for radical surgery (Colectomy) following successful endoscopic resection (EMR/ESD) of a malignant polyp
Macro-morphology Rule
The choice of staging system depends on whether the polyp was Pedunculated (Haggitt) or Sessile/Flat (Kikuchi).
How it Works
Haggitt Levels (For Pedunculated Polyps)
01
Level 1: Invasion limited to the head of the polyp.
02
Level 2: Invasion involving the neck of the polyp.
03
Level 3: Invasion involving any part of the stalk.
04
Level 4: Invasion into the submucosa of the underlying bowel wall.
Kikuchi Levels (For Sessile/Flat polyps)
01
Sm1: Invasion into the upper third of the submucosa.
02
Sm2: Invasion into the middle third.
03
Sm3: Invasion into the lower third (near the muscularis propria).
The 1000 µm Threshold
Because "thirds" are subjective on small biopsies, modern pathology often uses absolute depth: > 1000 µm $(1 mm)$ of submucosal invasion is considered "deep" (Sm2/3) and carries a high risk of LNM.
Clinical Pearls
Risk of Lymph Node Metastasis (LNM)
| Haggitt 1–3 | Low Risk (< 1%) |
| Haggitt 4 / Sm3 | High Risk (15–25%) |
| Sm1 (< 1000 µm) | Moderate Risk (~1–3%) |
When is Endoscopic Resection NOT Curative?
Endoscopic resection is considered "non-curative" if ANY of the following are met: 1) Sm2/3 or > 1000µm invasion, 2) Poor differentiation (G3), 3) Lymphovascular invasion (LVI), 4) High-grade tumour budding, or 5) Margin < 1 mm.
Clinical Pearls
Haggitt 4 is biologically equivalent to a sessile Sm lesion because the invasion has reached the "true" bowel wall
Pedunculated polyps (Haggitt 1-3) can almost always be managed conservatively after successful snare excision
Sessile lesions (Sm1) may require surgery if other high-risk features like LVI are present
Next Steps
Management Decisions
01
Low Risk (Haggitt 1-3 AND no LVI): Surveillance colonoscopy in 3–6 months.
02
High Risk (Sm2/3 or LVI+): Oncological resection (Segmental Colectomy) with lymphadenectomy.
The Evidence
Foundational Haggitt
Prognostic factors in colorectal carcinomas arising in adenomas: implications for lesions removed by endoscopic polypectomy.
Haggitt RC et al. • Gastroenterology. 1985;89(2):328-36. The primary stalk-staging paper.
View Source• . ;
Foundational Kikuchi
Management of early invasive colorectal cancer. Risk of recurrence and clinical guidelines.
Kikuchi R et al. • Int J Colorectal Dis.. 1995;Establishing the Sm1-3 thirds system.
View SourceOrigins & History
Pathology Leaders
Rodger Haggitt (USA) and Ryoji Kikuchi (Japan) developed these systems independently to answer the same desperate clinical question: "Now that we have removed the cancer endoscopically, is it safe to leave the patient alone?" Their scales remain the global surgical anchors for T1 disease.
Last Comprehensive Review: 2026-07-17