Table 4.
Two Systems of Classification of Thyroid Tumors by Ki-67 Labeling Index
| WHO classification [2] | Prognostic classification proposed by Kakudo et al. [101] | ||
|---|---|---|---|
| Tumors | Ki-67 | Tumors | Ki-67 |
| Benign | |||
| Normal thyroid follicular cells | <3% | Follicular adenoma | <3% |
| Borderline tumorsa, encapsulated tumors | |||
| WDT-UMP, FT-UMP, NIFTP, NEPRAS, noninvasive encapsulated PTC, minimally invasive FTC (capsular invasion only) | <3% | ||
| Borderline tumors, non-encapsulated (infiltrative) tumors | |||
| Well-differentiated thyroid carcinoma | <10% | Papillary microcarcinoma | <3% |
| Malignant tumors (invasive carcinoma, >1 cm) | |||
| Low risk invasive | ≤5% | ||
| Moderate risk | 5%–10% | ||
| Poorly differentiated carcinoma | 10%–30% | High risk | 10%–30% |
| Anaplastic thyroid carcinoma | > 30% | Anaplastic thyroid carcinoma | >30% |
WHO, World Health Organization; WDT-UMP, well-differentiated tumor of uncertain malignant potential; FT-UMP, follicular tumor of uncertain malignant potential; NIFTP, noninvasive follicular thyroid neoplasm with papillary like nuclear features; NEPRAS, noninvasive encapsulated papillary RAS-like thyroid tumor; PTC, papillary thyroid carcinoma; FTC, follicular thyroid carcinoma.
a
Borderline tumors were defined as tumors with T1N0M0 stage and without extrathyroidal extension.