| Group | Tumor size(cm) | Mitotic Rate (per 50HPFs) | Gastric GISTs | Small intestinal GISTs |
| 1 | £2 | ≤5 | Very low or none | Very low or none |
| 1 | >2 to ≤5 | £5 | Low | Low |
| 3a | >5 to ≤10 | ≤5 | Low | Intermediate |
| 3b | >10 | ≤5 | Intermediate | High |
| 4 | ≤2 | >5 | Low | High |
| 5 | >2 to ≤5 | >5 | Intermediate | High |
| 6a | >5 to ≤10 | >5 | High | High |
| 6b | >10 | >5 | High | High |