Classification of the severity of duodenal polyposis as per Spigelman score35
| Duodenal disease grading (points) | |||
| 1 | 2 | 3 | |
| Number of polyps | 1–4 | 5–20 | >20 |
| Size of polyps (mm) | 1–4 | 5–10 | >10 |
| Histology | Tubular | Tubulovillous | Villous |
| Dysplasia | Low | – | High |
Stage 0, 0 points; stage I, 1–4 points; stage II, 5–6 points, stage III, 7–8 points; stage IV, 9–12 points.