Head & Neck

Thyroid Cancer

Includes illustrated staging details

The thyroid is a butterfly-shaped gland below the larynx (voice box) in the front of the neck. It produces hormones that help regulate heart rate, body temperature, growth and metabolism. Four parathyroid glands (not shown) are pea-sized organs on the back of the thyroid. They produce hormones that control blood calcium levels.



Thyroid tissues contain two types of cells. Follicular cells produce the thyroid hormone, and parafollicular cells (commonly called C-cells) produce a hormone involved in processing calcium.



Papillary thyroid cancer is the most common of the four primary types of thyroid cancer. It begins in the follicular cells, as does follicular thyroid cancer. Both are called well-differentiated cancers because their cells look similar to healthy thyroid cells when viewed under a microscope. They tend to spread and grow slowly. Medullary thyroid cancer begins in the C-cells and is more aggressive than papillary and follicular thyroid cancer. Anaplastic thyroid cancer is called undifferentiated or poorly differentiated because its cells look very different from healthy thyroid cells. Anaplastic thyroid cancer tends to grow and spread very quickly. It is the most aggressive form of thyroid cancer.



Thyroid cancer is often not accompanied by many symptoms. It is sometimes discovered on imaging scans or other tests performed to diagnose another medical condition.


    Treatment Options

    Your treatment plan will be based on the type and stage of the thyroid cancer as well as your age, overall health, symptoms, previous treatments and preferences for quality of life. One or more of the following therapies may be recommended.



    Surgery is the most common treatment for thyroid cancer, and various procedures and techniques may be available.



    Lobectomy, also called hemithyroidectomy, may be used in some low-risk cases when only half of the thyroid needs to be removed.



    Near-total thyroidectomy is used to remove all but a very small part of the thyroid. Some lymph nodes may also be removed.



    Total thyroidectomy removes the entire thyroid gland. As a result, thyroid hormone therapy must be taken because thyroid hormones can no longer be produced in the body. This hormone replacement medication can be taken as a pill. Taking calcium and vitamin D supplements may be necessary if the parathyroid gland function is affected by surgery. Your surgeon may also remove lymph nodes in the neck to see if the cancer has spread.



    Radioactive iodine treatment can be used to destroy remaining thyroid cells that were not removed by surgery or that have spread beyond what can be removed with surgery. This involves giving radioactive iodine (I-131) in liquid or pill form. The thyroid absorbs almost all iodine that enters the body. The radioactive iodine will concentrate in any remaining thyroid tissue, and the radiation will kill the cancer cells.



    This treatment is standard of care for papillary or follicular thyroid cancer that has spread to lymph nodes in the neck or other parts of the body. Radioactive iodine treatment does not work in medullary thyroid cancer or anaplastic thyroid cancer because the cancer cells do not absorb iodine.



    Radiation therapy is usually given after surgery as adjuvant therapy and concentrates on targeted cancer cells in a specific area. It is more often used as part of treatment for medullary and anaplastic thyroid cancer. External-beam radiation therapy is used typically for later stage thyroid cancer that has spread to critical areas of the neck, such as the trachea, voice box or esophagus.



    Drug therapy is systemic therapy that travels throughout the body and may include chemotherapy, hormone therapy or targeted therapy.



    Chemotherapy uses drugs to destroy cancer cells by preventing them from growing and dividing. It may consist of a single drug or multiple drugs given in combination. It may also be combined with other types of treatment.



    Hormone therapy is used after surgery that removes part of or the whole thyroid. It replaces the hormone needed by the body. It may also slow the growth of remaining differentiated cancer cells.



    Targeted therapy drugs are used to slow or stop the progression of disease in certain types of thyroid cancer. Two types of targeted therapy approved for thyroid cancer include tyrosine kinase inhibitors, which block signals needed for tumors to grow, and protein kinase inhibitors, which block proteins needed for cell growth and may kill cancer cells. They may be an option if specific molecular (genetic) abnormalities are found in the tumor. Some of these abnormalities include a neurotrophic tyrosine receptor kinase (NTRK) genetic fusion, a BRAF V600E gene mutation and RET mutation-positive cancers. In some cases, targeted therapy may be used to treat certain types of metastatic thyroid cancer.



    Watchful waiting is a strategy of postponing treatment to avoid potential treatment side effects as long as possible. It may be recommended for tumors that appear to be growing very slowly. Your doctor will closely monitor you for signs the cancer has progressed or returned before starting treatment.


    Staging

    Diagnosing your type of thyroid cancer is an important step in creating the best treatment plan for you. Your doctor will perform a thorough exam, imaging studies, blood tests and a biopsy and use these test results to stage the cancer. Staging determines the extent of your cancer, where it is located and whether it has metastasized (spread) to nearby organs, tissues or lymph nodes, or to other parts of your body.

    The TNM staging system, developed by the American Joint Committee on Cancer (AJCC), is typically used to classify and stage thyroid cancer. This system classifies the cancer by tumor (T), node (N) and metastasis (M). The T category describes the size and location of the primary tumor. The N category indicates whether the lymph nodes show evidence of cancer cells. The number and location of these lymph nodes are important because they show how far the disease has spread. The M category describes metastasis (spread of cancer to another part of the body), if any.

    Staging Criteria

    Once the cancer is classified, an overall stage is assigned. Thyroid cancer may be Stage I through Stage IV. Stages I and II are generally confined to the local area where the cancer is found, and Stage III has spread to the regional lymph nodes in the neck. Stage IV is further divided into Stages IVA, IVB and IVC. Stages IVA and IVB are locally or regionally advanced disease, and Stage IVC has spread to distant sites, such as the liver, lungs or bone.

    These basic stages are designed to group patients who have a similar prognosis (outlook). This grouping allows doctors to more accurately predict outcomes for patients depending on the type of treatment they receive. In certain cancers, the stage is also determined by other factors. For thyroid cancer, the subtype of cancer and age of the patient may influence the stage.

    Sometimes your doctor may reassess your stage after treatment or if cancer recurs. This is known as restaging. It is rarely done but typically involves the same diagnostic tests used for the original staging. If a new stage is assigned, it’s often preceded by an “r” to denote that it’s been restaged and different from the original stage given at diagnosis.

    Look carefully at the table headlines and sections to ensure you view the information that applies to your diagnosis as each has unique staging characteristics.

    TNM Classification for Thyroid Cancer

    Classification Definition
    Tumor (T)
    TX Primary tumor cannot be assessed.
    T0 No evidence of primary tumor.
    Anaplastic & Differentiated
    T1 Tumor ≤ (not more than) 2 cm in greatest dimension limited to the thyroid.
      T1a Tumor ≤ (not more than) 1 cm in greatest dimension limited to the thyroid.
      T1b Tumor > (more than) 1 cm but ≤ (not more than) 2 cm in greatest dimension limited to the thyroid.
    T2 Tumor > (more than) than 2 cm but ≤ (not more than) 4 cm in greatest dimension limited to the thyroid.
    T3 Tumor > (more than) 4 cm limited to the thyroid, or gross extrathyroidal extension (extended beyond the thyroid) invading only strap muscles.
      T3a Tumor > (more than) 4 cm limited to the thyroid.
      T3b Gross extrathyroidal extension (extended beyond the thyroid) invading only strap muscles (sternohyoid, sternothyroid, thyrohyoid or omohyoid muscles) from a tumor of any size.
    T4 Includes gross extrathyroidal extension (extended beyond the thyroid) beyond the strap muscles.
      T4a Gross extrathyroidal extension (extended beyond the thyroid) invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve from a tumor of any size.
      T4b Gross extrathyroidal extension (extended beyond the thyroid) invading prevertebral fascia or encasing the carotid artery or mediastinal vessels from a tumor of any size.
    Medullary
    T1 Tumor is ≤ (not more than) 2 cm in greatest dimension limited to the thyroid.
      T1a Tumor is ≤ (not more than) 1 cm in greatest dimension limited to the thyroid.
      T1b Tumor is > (more than) 1 cm but ≤ (not more than) 2 cm in greatest dimension limited to the thyroid.
    T2 Tumor is > (more than) 2 cm but ≤ (not more than) 4 cm in greatest dimension limited to the thyroid.
    T3 Tumor is > (more than) 4 cm or with extrathyroidal extension (extended beyond the thyroid).
      T3a Tumor is > (more than) 4 cm in greatest dimension limited to the thyroid.
      T3b Tumor of any size with gross extrathyroidal extension (extended beyond the thyroid) invading only strap muscles (sternohyoid, sternothyroid, thyrohyoid or omohyoid muscles).
    T4 Advanced disease.
      T4a Moderately advanced disease; tumor of any size with gross extrathyroidal extension (extended beyond the thyroid) into the nearby tissues of the neck, including subcutaneous soft tissue, larynx, trachea, esophagus or recurrent laryngeal nerve.
      T4b Very advanced disease; tumor of any size with extension toward the spine or into nearby large blood vessels, gross extrathyroidal extension (extended beyond the thyroid) invading the prevertebral fascia, or encasing the carotid artery or mediastinal vessels.
    Node (N)
    NX Regional lymph nodes cannot be assessed.
    N0 No evidence of locoregional lymph node metastasis.
      N0a One or more cytologically (based on fine needle aspiration biopsy) or histologically (based on pathologic analysis of tissues after surgery) confirmed benign lymph nodes.
      N0b No radiologic or clinical evidence of locoregional lymph node metastasis.
    N1 Metastasis to regional nodes.
      N1a Metastasis to level VI or VII (pretracheal, paratracheal, or prelaryngeal/Delphian, or upper mediastinal) lymph nodes. This can be unilateral (on one side) or bilateral (on both sides) disease.
      N1b Metastasis to unilateral (on one side), bilateral (on both sides), or contralateral (opposite side of thyroid tumor) lateral lymph nodes (levels I, II, III, IV or V) or retropharyngeal lymph nodes.
    Metastasis (M)
    M0 No distant metastasis.
    M1 Distant metastasis.

    Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

    Staging Anaplastic Thyroid Cancer

    Stage T N M
    IVA T1 - T3a N0/NX M0
    IVB T1 - T3a
    T3b, T4
    N1
    Any N
    M0
    M0
    IVC Any T Any N M1

    Illustrated Stages of Anaplastic Thyroid Cancer

    Staging Differentiated Thyroid Cancer*

    Stage T N M
    Younger than 55 years
    I Any T Any N M0
    II Any T Any N M1
    55 years or older
    I T1, T2 N0, NX M0
    II T1, T2
    T3a, T3b
    N1
    Any N
    M0
    M0
    III T4a Any N M0
    IVA T4b Any N M0
    IVB Any T Any N M1

    *Includes papillary, follicular, poorly differentiated and Hurthle cell carcinoma

    Illustrated Stages of Differentiated Thyroid Cancer (younger than 55)

    Illustrated Stages of Differentiated Thyroid Cancer (55 and older)

    Staging Medullary Thyroid Cancer

    Stage T N M
    I T1 N0 M0
    II T2, T3 N0 M0
    III T1 - T3 N1a M0
    IVA T4a
    T1 - T3
    Any N
    N1b
    M0
    M0
    IVB T4b Any N M0
    IVC Any T Any N M1

    Illustrated Stages of Medullary Thyroid Cancer

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