A patient’s prognosis varies greatly based on the type of cancer and how far it has spread. Staging enables a physician to determine a patient’s prognosis and choose the most appropriate treatment methods.

The TNM system of the American Joint Committee on Cancer (AJCC) is the most common system used to stage cancer. When used to stage thyroid cancer, this system includes:

• T describes the primary tumor (e.g., size, location)
  
  
• N describes whether or not the cancer has spread to neighboring lymph nodes
  
  
• M describes whether or not there are distant metastases (spread of cancer to distant parts of the body)

Information about all three of these factors are combined to assign a stage, in a process called stage grouping. Typically the stages are described by Roman numerals I to IV. Unlike many other cancers, thyroid cancers are classified into stages using a method that takes into account the type of cancer and the patient’s age.

Stage grouping for papillary carcinoma or follicular thyroid carcinoma:

Patients under age 45

• Stage I. The tumor can be any size. It may or may not have spread within the neck or upper chest and/or to nearby lymph nodes, but has not spread to distant sites.
  
  
• Stage II. The tumor can be any size. It may or may not have spread to lymph nodes, but has spread to distant sites such as the lung or bone.

Patients age 45 and older

• Stage I. The tumor is 2 centimeters ([cm], about ¾ inch or smaller), and has not spread.
  
  
• Stage II. The tumor is between 2 and 4 cm (¾ and 1½ inches) and has not spread.
  
  
• Stage III. Either:
  
  
• • The tumor is larger than 4 cm (1½ inches) or has grown just outside the thyroid gland and has not spread
    
    
  • The tumor is any size and has spread to neighboring lymph nodes in the neck but not to distant sites.
    
    
• Stage IV. Either:
  
  
• • The tumor is any size and has grown beyond the thyroid gland to invade neighboring tissues, and may or may not have spread to nearby lymph nodes in the neck or upper chest, but not to distant sites.
    
    
  • The tumor has either grown back toward the spine or into neighboring large blood vessels in the neck or upper chest. It may or may not have spread to the lymph nodes, but has not spread to distant sites.
    
    
  • The tumor is any size. It may or may not have spread to lymph nodes, but has spread to distant sites such as the lung or bone.

Stage grouping for medullary thyroid carcinoma (MTC):

• Stage 0. No tumor is found in the thyroid gland, but screening tests detect the cancer. This stage is also known as carcinoma in situ (early cancer that has not spread to nearby tissues).
  
  
• Stage I. The tumor is 2 cm (3/4 inch) or smaller and has not spread.
  
  
• Stage II. The tumor is between 2 and 4 cm (3/4 and 1½ inches) and has not spread.
  
  
• Stage III. Either:
  
  
• • The tumor is larger than 4 cm (1½ inch) or has grown just outside the thyroid gland and has not spread
    
    
  • The tumor is any size and has spread to neighboring lymph nodes in the neck but not to distant sites.
    
    
• Stage IV. Either:
  
  
• • The tumor is any size and has grown beyond the thyroid gland to invade neighboring tissues, and may or may not have spread to nearby lymph nodes in the neck or upper chest, but not to distant sites.
    
    
  • The tumor is any size and has either grown back toward the spine or into neighboring large blood vessels in the neck or upper chest. It may or may not have spread to the lymph nodes, but has not spread to distant sites.
    
    
  • The tumor is any size. It may or may not have spread to lymph nodes, but has spread to distant sites such as the lung or bone.

Stage grouping for anaplastic carcinoma:

All anaplastic thyroid cancers are considered to be stage IV, either:

• The tumor is any size and has grown beyond the thyroid gland to invade neighboring neck tissues. It may or may not have spread to nearby lymph nodes in the neck but not to distant sites.
  
  
• The tumor is any size and has grown back toward the spine or into neighboring large blood vessels in the neck or upper chest. It may or may not have spread to lymph nodes, but has not spread to distant sites.
  
  
• The tumor is any size. It may or may not have spread to lymph nodes but has spread to distant sites such as the lung or bone.

According to the American Cancer Society (ACS), the five-year survival rate for patients in the different stages of thyroid cancer includes:

Five-Year Relative Survival Rates