Table 1: Risk of death from thyroid cancer [5].

Very low riskLow riskIntermediate riskHigh risk

Age at diagnosis<45 years<45 yearsYoung patients (<45 years)
Classic PTC >4 cm
Vascular invasion
Extrathyroidal extension
Worrisome histology of
any size
>45 years

Primary tumor size<1 cm1–4 cmOlder patients (>45 years)
Classic PTC <4 cm
Extrathyroidal extension
Worrisome histology
<1-2 cm confined to the
>4 cm classic PTC

HistologyClassic PTC, confined to the thyroid gland*Classic PTC, confined to
the thyroid gland*
Histology in conjunction with age as aboveWorrisome histology
>1-2 cm

Completeness of resectionComplete resectionComplete resectionComplete resectionIncomplete tumor resection

Lymph node involvementNone apparentPresent or absentPresent or absentPresent or absent

Distant metastasisNone apparentNone apparentNone apparentPresent

Only those patients meeting all criteria within the respective column would be classified as very low risk or low risk. Older patients with either incomplete tumor resection or presence of distant metastasis are considered high risk irrespective of tumor size and specific histology. Patients with a combination of risk factors (age, histology, and tumor size) crossing over between columns are classified as intermediate-risk patients. PTC: papillary thyroid cancer.
*Confined to the thyroid gland with no evidence of vascular invasion or extrathyroidal extension.
Cervical lymph node metastases in older patients, but probably not in younger patients, may confer an increased risk of death from disease.
Worrisome histologies include histologic subtypes of papillary thyroid cancer such as tall cell variant, columnar variant, insular variant, and poorly differentiated thyroid cancers.