Staging & Prognosis

T Stage – size of the thyroid cancer and has it grown into nearby structures.

• T1: 2.0 cm.
• T2: > 2.0 cm but ≤ 4.0 cm.
• T3: > 4.0 cm but confined to the thyroid, or any size tumor and gross invasion into the strap muscles (muscles overlying the thyroid gland).
• T4: Any size tumor invading structures of the neck including (trachea, larynx, esophagus, or recurrent laryngeal nerve).

N Stage – extent of lymph node involvement in the neck by compartment.

• N0: no lymph node involvement.
• N1a: involvement of lymph node(s) in the central neck (between the trachea and the carotid artery) compartment.
• N1b: involvement of lymph node(s) in the lateral neck compartment (anything lateral to, or on the other side of, the carotid artery).

M Stage – Presence of distant metastases (spread beyond the neck).

• M0: No distant metastases.
• M1: + distant metastases.

< 55 years of age:

• Stage I
  • Any T (any size of cancer, T1, T2, T3a; or if invading nearby structures, T3b or T4).
  • With (N1a or N1b) or without (N0) spread to lymph nodes in the neck.
  • Has not spread to a distant part of the body beyond the neck (M0).
• Stage II
  • Any T, any N, the cancer has spread to a distant part of the body beyond the neck (M1).

≥ 55 years of age:

• Stage I
  • T1 (largest tumor ≤ 2.0 cm) or T2 (> 2.0 cm but ≤ 4.0 cm).
  • No spread to lymph nodes in the neck (N0).
  • No spread beyond the neck (M0).
• Stage II
  • T1 (largest tumor ≤ 2.0 cm) or T2 (> 2.0 cm but ≤ 4.0 cm).
  • + spread to lymph nodes in the neck (N1).
  • No spread beyond the neck (M0).
    Or
  • T3a (≥ 4.0 cm) or T3b (any size but has grossly invaded the strap muscles overlying the thyroid).
  • With (N1a or N1b) or without (N0) spread to lymph nodes in the neck.
  • No spread beyond the neck (M0).
• Stage III
  • T4a (any size but the cancer has extensively invaded the structures nearby (larynx, trachea, esophagus, or recurrent laryngeal nerve).
  • With (N1a or N1b) or without (N0) spread to lymph nodes in the neck.
  • No spread beyond the neck (M0).
• Stage IVa
  • T4b (any size but the cancer has grown extensively to invade the spine or the large blood vessels in the neck – carotid artery).
  • With (N1a or N1b) or without (N0) spread to lymph nodes in the neck.
  • No spread beyond the neck (M0).
• Stage IVb
  • Any T.
  • Any N.
  • M1 (cancer has spread to a distant part of the body beyond the neck).

Based on staging of the cancer, prognosis can be predicted with 10 year expected survival rates.

• How many patients will not die from their thyroid cancer 10 years following treatment?
  • Stage I
    • 98-100%
  • Stage II
    • 85-95%
  • Stage III
    • 60-70%
  • Stage IV
    • < 50%
• Overall, the prognosis of WDTC’s remains excellent with Stage I and II cancers.
  • Poor prognosis begins when cancer:
    • Grossly invades nearby structures such as larynx (voice box), trachea, esophagus (food pipe), and recurrent laryngeal nerve (controls the movement of the vocal cord and voice).
    • Invades the spine deep in the neck or the carotid artery on the side of the neck.
    • Has spread distantly to a site in the body beyond the neck.

Predicting risk for cancer recurrence immediately after surgery using the American Thyroid Association Risk Stratification System.

• This is different from the above 10-year expected survival rates.
  • If the cancer returns, it does not mean it will cause death (especially within 10 years of initial treatment).
    • Cancer recurrence can still be treated with a high rate of cure if limited to the neck.
• Uses information specific to the pathology report to predict if there will be persistent cancer following surgery.
• Helps to guide decision making on radioactive iodine (RAI) and frequency of surveillance.
  • Low risk (1-5% risk for recurrence; accounts for ~54% of thyroid cancers).
    • Cancer remains completely inside the thyroid (intrathyroidal; not invading through the capsule into nearby structures).
    • < 2.0 cm (1-2%).
    • > 2.0 but < 4.0 cm (5%).
    • Multifocal disease (multiple sites of cancer inside the thyroid, ~5%).
    • < 5 lymph nodes with spread of cancer (5%).
    • Size of cancer focus inside of any lymph node < 0.2 cm (5%).
    • Follicular variant of PTC encapsulated or with minimal capsular invasion (1-2%).
    • FTC with capsular invasion and no or minimal vascular invasion (< 4 vessels involved).
  • Intermediate risk (5-30% risk for recurrence; accounts for ~38% of thyroid cancers).
    • Aggressive histology:
      • Tall cell, hobnail, columnar cell, diffuse sclerosing, and solid variants of Papillary Thyroid Cancer (PTC).
    • Minor invasion into the strap muscles (extrathyroidal extension) (3-8%).
    • ≥ 4.0 cm (8-10%).
    • > 5 lymph nodes with spread of cancer (20%).
    • Size of cancer focus inside of any lymph node > 0.2 cm but < 3.0 cm (20%).
    • Lymph node felt on exam prior to surgery (clinical N1) (20%).
    • PTC with vascular invasion (15-30%).
  • High risk (30-55% risk for recurrence; accounts for ~8% of thyroid cancers).
    • Size of cancer focus inside of any lymph node ≥ 3.0 cm (30%).
    • Gross invasion into the strap muscles (extrathyroidal extension) (30-40%).
    • Cancer invading through the capsule of the lymph node (extranodal extension) (40%).
    • TERT mutation present (>40%).
    • FTC with extensive vascular invasion (> 4 vessels) (30-55%).
    • Incomplete resection / Positive margin (known cancer left behind).
    • Distant metastasis.
• Patients with intermediate or high risk for risk recurrence should consider RAI following surgery and should be watched more frequently than low risk patients during the 5-year surveillance period.