Fig. 1Approach to low-risk papillary thyroid cancer (PTC). RAI, radioactive iodine.
Table 1ATA 2009 Risk Stratification System with Proposed Modifications for Structural Disease Recurrence in Differentiated Thyroid Cancer
ATA low-risk |
ATA intermediate risk |
ATA high risk |
PTC with all of the following: |
Microscopic ETE |
Gross ETE |
No local or DM |
RAI-avid metastatic foci in the neck on the first post-treatment WBS |
Incomplete tumor resection |
All macroscopic tumor has been resected |
Aggressive cyto-type (e.g., tall cell, hobnail variant, columnar cell carcinoma) |
Distant metastases |
No tumor invasion of loco-regional tissues or structures |
PTC with vascular invasion |
Postoperative serum thyroglobulin suggestive of DM |
No aggressive cyto-type (e.g., tall cell, hobnail variant, columnar cell carcinoma) |
Clinical N1 or >5 pathologic N1 with all involved LN <3 cm in largest dimension |
Pathologic N1 with any metastatic LN ≥3 cm in largest dimension |
If RAI given, there are no RAI-avid metastatic foci outside the thyroid bed on the first post treatment WBS |
Multifocal PMC with ETE and BRAFV600E mutated (if known) |
FTC with extensive vascular invasion (>4 foci of vascular invasion) |
No vascular invasion |
|
|
Clinical N0 or ≤5 pathologic N1 micro-metastases (<0.2 cm in largest dimension) |
|
|
Intra-thyroidal EFVPTC |
|
|
Intra-thyroidal WD-FTC with capsular invasion and no or minimal (<4 foci) vascular invasion |
|
|
Intra-thyroidal PMC, unifocal or multifocal, including BRAFV600E mutated (if known) |
|
|
Table 2The Expanded Definition of Low-Risk Thyroid Cancer
Previous features of low-risk thyroid cancer [20] |
New features of low-risk thyroid cancer [79] |
Low-risk for recurrence |
Low-risk for recurrence |
PTC with all of the following: |
All previous features of low-risk for recurrence PTC |
No local or DM |
PTC with: clinical N0 or ≤5 pathologic N1 micro-metastases (<0.2 cm in largest dimension) |
All macroscopic tumor has been resected |
Intra-thyroidal EFVPTC |
No tumor invasion of loco-regional tissues or structures |
Intra-thyroidal WD-FTC with capsular invasion and no or minimal (<4 foci) vascular invasion |
No aggressive cyto-type (e.g., tall cell, hobnail variant, columnar cell carcinoma) |
Intra-thyroidal PMC, unifocal or multifocal, including BRAFV600E mutated (if known) |
If RAI given, there are no RAI-avid metastatic foci outside the thyroid bed on the first post treatment WBS |
Low-risk for mortality |
No vascular invasion |
Age cut-off <55 years of age at diagnosis |
|
Minor ETE detected only on histological examination has no impact on either T category or overall stage |
|
T3a tumors >4 cm confined to the thyroid gland, any N, M0 |
|
T3b tumor of any size with gross ETE into strap muscles only (sternohyoid, sternothyroid, thyrohyoid, or omohyoid muscles), any N, M0 |
|
Very low-risk tumors |
|
PMC with no evidence of ETE nor metastases |
Table 3Clinical Framework: Risk Stratification Approach to Decision Making in Probable or Proven Papillary Microcarcinoma
Candidates for observation |
Tumor and neck US findings |
Patient features |
Medical team features |
Ideal |
Single thyroid nodule Well-defined margins |
Older individuals (<60 years) |
Experienced multidisciplinary team |
Surrounded by 2+ mm of normal thyroid parenchyma |
Willing to accept an active surveillance approach |
High-quality neck US performed by skilled radiologist |
No evidence of ETE |
Understands that a surgical intervention might be necessary in the future |
Prospective data collection |
Previous US with stability |
Expected to be compliant with FU plans |
Tracking or reminder program to ensure proper FU |
cN0 |
Supportive significant others |
|
cM0 |
Life-threatening comorbidities |
|
Appropriate |
Multifocal PMC |
Young adults and middle-aged patients (18–59 years) |
Experienced endocrinologist or thyroid surgeon |
Subcapsular locations not adjacent to RLN without evidence of ETE |
Strong FH of PTC |
Neck US routinely available |
Ill-defined margins |
Child bearing potential |
|
Background US findings that will make FU difficult (thyroiditis, nonspecific LNs, multiple, other benign-appearing thyroid nodules) |
|
|
FDG avid PMC |
|
|
Inappropriate |
Evidence of aggressive cytology on FNA (rare) |
Children and adolescents (<18 years of age) |
Reliable neck US not available |
Subcapsular locations adjacent to RLN |
Unlikely to be compliant with FU plans |
Little experience with TC management |
Evidence of ETE |
Not willing to accept an observation approach |
|
Clinical evidence of invasion of RLN or trachea (rare) |
|
|
N1 disease at initial evaluation or identified during FU |
|
|
M1 disease (very rare) |
|
|
Definitive increase in size of ≥3 mm in a confirmed PTC tumor |
|
|
Table 4Active Surveillance Studies
|
Japan: Ito et al. (2014) [22] |
Japan: Sugitani et al. (2010) [24] |
USA: Tuttle et al. (2017) [28] |
No. of patients |
1,235 |
230 Patients and 300 lesions |
291 |
Tumor size cut-off, cm |
≤1 |
≤1 |
≤1.5 |
Time of follow-up |
Mean, 6.25 years (range, 1.5–18.91) |
Mean, 5 years (range, 1–17) |
Median, 25 months (range, 6–166) |
At 10 year observation |
Ultrasound surveillance |
1–2/year |
1–2/year |
2/year for 2 years then 1/year |
Tumor increase by ≥3 mm, % |
8 |
7 |
3.8 |
Novel lymph node metastases, % |
3.8 |
1 |
0 |