Staging is the process of finding out if and how far a cancer has spread. Medullary thyroid cancer staging is a critical factor in choosing medullary thyroid cancer treatment treatments, medullary thyroid cancer extent of surgery, and predicting your chance for cure.

How is Medullary Thyroid Cancer Staged?

Medullary thyroid cancer staging is based on the results of the physical examination, biopsy, imaging tests (ultrasound, CT scans, MRIs, chest x-ray, and/or PET scans [which are described in the section Diagnosis of Medullary Thyroid Cancer]) and the pathologic findings of surgery itself .

The size of the medullary thyroid cancer within the thyroid gland itself and whether or not the cancer has spread into lymph nodes around the thyroid or sides of the neck is also included in the medullary thyroid staging system. The medullary thyroid cancer staging system also includes whether or not the cancer has spread into the fat and muscles around the thyroid (called local extension). Even further, the staging system includes whether the cancer has invaded into structures such as the breathing tube (trachea), voice box (larynx), or esophagus. The last component of medullary thyroid cancer staging is the presence of distant metastases, which means whether the cancer has spread to distant (far away) areas like the lungs, bone or liver.

Note, the more common differentiated thyroid cancers, papillary thyroid cancer and follicular thyroid cancer are also staged based upon the age of the patient at diagnosis. In medullary thyroid cancer, age does not play any role in staging of this thyroid cancer.

In medullary thyroid cancer staging, and for that matter all cancer staging, the earlier the stage of disease is the more favorable and curable the cancer. Therefore, the lower/smaller the number, the better the chance for cure and long term survival.

The Medullary Thyroid Cancer TNM staging system

A staging system is a standard way to sum up how large a cancer is and how far it has spread.

The most common system used to describe the stages of thyroid cancer is the American Joint Committee on Cancer (AJCC) TNM system. The TNM system is based on 3 key pieces of information:

  • Tindicates the size of the main (primary) tumor and whether it has grown into nearby areas.
  • N describes the extent of spread to nearby (regional) lymph nodes. Lymph nodes are bean-shaped collections of immune system cells to which cancers often spread first. Cells from thyroid cancers can travel to lymph nodes in the neck and chest areas.
  • M indicates whether the cancer has spread (metastasized) to other organs of the body. (The most common sites of spread of thyroid cancer are the lungs, the liver, and bones.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity. The letter X means a category can't be assessed because the information is not available.

T categories for medullary thyroid cancer (does not include anaplastic thyroid cancer)

TX: Primary tumor cannot be assessed.

T0: No evidence of primary tumor.

T1: The tumor is 2 cm (slightly less than an inch) across or smaller and has not grown out of the thyroid.

  • T1a: The tumor is 1 cm (less than half an inch) across or smaller and has not grown outside the thyroid.
  • T1b: The tumor is larger than 1 cm but not larger than 2 cm across and has not grown outside of the thyroid.

T2: The tumor is more than 2 cm but not larger than 4 cm (slightly less than 2 inches) across and has not grown out of the thyroid.

T3: The tumor is larger than 4 cm across, or it has just begun to grow into nearby tissues outside the thyroid.

T4a: The tumor is any size and has grown extensively beyond the thyroid gland into nearby tissues of the neck, such as the larynx (voice box), trachea (windpipe), esophagus (tube connecting the throat to the stomach), or the nerve to the larynx. This is also called moderately advanced disease.

T4b: The tumor is any size and has grown either back toward the spine or into nearby large blood vessels. This is also called very advanced disease.

N categories for papillary thyroid cancer

NX: Regional (nearby) lymph nodes cannot be assessed.

N0: The cancer has not spread to nearby lymph nodes.

N1: The cancer has spread to nearby lymph nodes.

  • N1a: The cancer has spread to lymph nodes around the thyroid in the neck (called pretracheal, paratracheal, and prelaryngeal lymph nodes).
  • N1b: The cancer has spread to other lymph nodes in the neck (called cervical) or to lymph nodes behind the throat (retropharyngeal) or in the upper chest (superior mediastinal).

M categories for thyroid cancer

MX: Distant metastasis cannot be assessed.

M0: There is no distant metastasis.

M1: The cancer has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc.

Stage grouping

Once the values for T, N, and M are determined, they are combined into stages, expressed as a Roman numeral from I through IV. Sometimes letters are used to further divide a stage. Remember, age plays no role in the staging of medullary thyroid cancer

Medullary Thyroid Cancer Stage Grouping:

Stage I (any T, any N, M0): Stage I (T1, N0, M0): The tumor is 2 cm or less across and has not grown outside the thyroid (T1). It has not spread to nearby lymph nodes (N0) or distant sites (M0).

Stage II (one of the following applies)

      T2, N0, M0: The tumor is more than 2 cm but is not larger than 4 cm across and has not grown outside the thyroid (T2). It has not spread to nearby lymph nodes (N0) or distant sites (M0).
      T3, N0, M0: The tumor is larger than 4 cm or has grown slightly outside the thyroid (T3), but it has not spread to nearby lymph nodes (N0) or distant sites (M0).

Stage III (T1 to T3, N1a, M0): The tumor is any size and might have grown slightly outside the thyroid (T1 to T3). It has spread to lymph nodes around the thyroid in the neck (N1a) but not to other lymph nodes or to distant sites (M0).

Stage IVA: One of the following applies:

      T4a, any N, M0: The tumor is any size and has grown beyond the thyroid gland and into nearby tissues of the neck (T4a). It might or might not have spread to nearby lymph nodes (any N). It has not spread to distant sites (M0).
      T1 to T3, N1b, M0: The tumor is any size and might have grown slightly outside the thyroid gland (T1 to T3). It has spread to certain lymph nodes in the neck (cervical nodes) or to lymph nodes in the upper chest (superior mediastinal nodes) or behind the throat (retropharyngeal nodes) (N1b), but it has not spread to distant sites (M0).

Stage IVB (T4b, Any N, M0): The tumor is any size and has grown either back toward the spine or into nearby large blood vessels (T4b). It might or might not have spread to nearby lymph nodes (any N), but it has not spread to distant sites (M0).

Stage IVC (Any T, Any N, M1): The tumor is any size and might or might not have grown outside the thyroid (any T). It might or might not have spread to nearby lymph nodes (any N). It has spread to distant sites (M1).