Table 1.
World Health Organization's clinical staging system for dogs with thyroid tumors.22
| Stage | Primary Tumor | Regional LN | Distant Metastases |
|---|---|---|---|
| I | T1 a,b | N0 | M0 |
| II | T0 | N1 | M0 |
| T1 a,b | N1 | M0 | |
| T2 a,b | N0 or N1 a | M0 | |
| III | T3 | Any N | M0 |
| Any T | N1 b or N2 b | M0 | |
| IV | Any T | Any N | M1 |
T0, microscopic residual disease; T1, <2 cm; T2, 2–5 cm; T3, >5 cm; N0, no lymph node involvement; N1, ipsilateral lymph node involvement; N2, bilateral lymph node involvement; M0, no evidence of distant metastases; M1, evidence of distant metastases; a, freely movable; b, fixed.