Thyroid Cancer Staging & Prognosis

This is mainly a summary of the 2007 BTA guidelines.

The principal factors contributing to risk of thyroid-cancer specific mortality are:
  • Older age, or cancer in young children
  • Male gender
  • Histology
    • papillary cancers generally have better prognosis than follicular cancers, though this may be due to confounding factors (age and tumour stage at diagnosis)
    • vascular invasion is associated with poorer prognosis
  • Tumour size
  • Extrathyroidal invasion
  • Metastasis
Staging systems are validated for cancer-specific survival. Orlov et al found that age, tumour size and TNM classification were not predictive of recurrence (defined by TSH-stimulated thyroglobulin elevation), but the De Groot system based on initial surgical pathology was:
  • Stage I - limited to thyroid gland
  • Stage II - LN involvement
  • Stage III - extrathyroidal invasion
  • Distant metastases

Jukkola found that just age>50 and extra-thyroidal invasion defined high risk of recurrence very accurately.

Recurrence most commonly occurs locally, i.e. cervical.

5th edition of TNM classification
Primary tumour
pT1 Intrathyroidal tumour, <=1cm greatest dimension
pT2 Intrathyroidal tumour, 1-4cm greatest dimension
pT3 Intrathyroidal tumour, >4cm greatest dimension
pT4 Any size extending beyond thyroid capsule
pTx Cannot be assessed
Regional lymph nodes (cervical or upper mediastinal)
N0 No nodes involved
N1 Regional nodes involved
   If possible, subdivide:
   N1a  Ipsilateral cervical nodes
   N1b  Bilateral, midline or contralateral cervical nodes or mediastinal nodes
NX Nodes cannot be assessed
Distant metastases
M0 No distant metastases
M1 Distant metastases
MX Metastases cannot be assessed
Papillary or follicular carcinoma staging
  Under 45 years 45 years and over
Stage 1 Any T, any N, M0 pT1, N0, M0
Stage 2 Any T, any N, M1 pT2, N0, M0
pT3, N0, M0
Stage 3   pT4, N0, M0
Any pT, N1, M0
Stage 4   Any pT, any N, M1

10 year mortality rates for differentiated (papillary and follicular) thyroid cancer
Stage 10-year cancer specific mortality
I 1.7%
II 15.8%
III 30%
IV 60.9%

MACIS score
Variable MACIS score component
Age <=39 years: 3.1
>=40 years: 0.08 x age
Tumour size 0.3 x diameter (cm)
Resection 1 if incomplete
Local invasion 1 if present
Distant metastases 3 if present
MACIS score and prognosis calculator

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