Type, Grade & Stage

Type

It is important to remember that not all lumps and bumps in the neck are cancer. Some thyroid nodules are benign (non-cancerous), and others are on the borderline between benign and malignant (cancerous). Often, the definitive diagnosis of the type of cancer is not fully determined until after the thyroid nodule has been surgically removed.  This is because a pathologist will need to examine the entire nodule within the thyroid gland before being able to determine for sure if the nodule is benign or malignant. 

Medullary Thyroid Cancer (MTC)

Overall this is a rare form of thyroid cancer, making up approximately 1-2% of all thyroid cancers. Medullary thyroid cancers (MTC) grow from cells in the thyroid called parafollicular cells. These cells produce the hormone calcitonin, which helps regulate calcium levels in the blood. Approximately 80% of medullary thyroid cancers are considered to be “sporadic cases,” meaning that the patients did not have a family history of MTC. The remaining 20% are cases of hereditary MTC, meaning that the disease is related to a genetic mutation that can be passed down from family members. In this heritable form of MTC, there is a mutation in a gene called the RET proto-oncogene, which can be detected with a blood test. This mutation is inherited in an autosomal dominant way, meaning that if one parent has the mutation, there is a 50% chance that each child will inherit the disease. MTC can also be associated with genetic syndromes such as MEN 2a and  MEN 2b, which generally appear at an earlier age and tend to be more aggressive. Learn more about the genetic syndromes that can lead to MTC.

Grade

Medullary thyroid carcinoma (MTC) is generally considered to be of low to intermediate grade. However, there is no formal grading system for MTC. 

Stage

The stage of a cancer is determined by the TNM staging system:

• The ‘T’ stands for tumor size.
• The ‘N’ stands for lymph node involvement.
• The ‘M’ stands for distant metastases, or cancer spread to other areas of the body.  

Staging helps doctors determine how serious the cancer is and how best to treat it. Staging systems often reference very specific anatomical structures. Please see the anatomy page to learn about these terms.

Staging is generally based on the American Joint Committee on Cancer (AJCC) 8th edition guidelines. To learn more, see the AJCC TNM Staging Table and the TNM Staging Tool below.