How Is Thyroid Cancer Diagnosed?
Most people who are eventually diagnosed with thyroid cancer first come to their doctor after noticing a lump in their neck, so the diagnostic process usually starts with an evaluation of this nodule. The first step is a medical history and physical exam from a medical professional. Blood and imaging tests for thyroid cancer may follow. A thyroid biopsy is used to confirm the diagnosis of thyroid cancer.
What Happens During the History and Physical Exam for Thyroid Cancer Diagnosis?
During the history, a medical professional will ask questions about risk factors like radiation exposure and thyroid cancer in other family members.
During the physical exam, a medical professional will check the thyroid nodule size, how firm it feels, and for swelling of nearby lymph nodes.
A medical professional will also ask and look for signs and symptoms of too much (hyperthyroidism) or too little (hypothyroidism) thyroid hormone activity (including changes in weight, changes in energy levels, and feeling too hot or too cold). These changes usually suggest that the thyroid nodule is NOT a cancer.
What Blood Tests Are Used For Thyroid Diagnosis?
Thyroid hormone levels can be measured from blood samples and used to help figure out if thyroid nodules are cancerous or not.
A hormone called TSH (Thyroid Stimulating Hormone) is checked to get a sense of overall thyroid activity. TSH is not actually made in the thyroid, but it helps regulate the production of other thyroid hormones. Most patients with thyroid cancer will have normal TSH levels.
Blood samples will also be checked for T3 & T4 (the metabolism-controlling hormones) and calcitonin (the calcium-controlling hormone). Most thyroid cancers will have normal T3 and T4 levels.
High calcitonin levels are often seen in medullary thyroid cancer. A blood protein called CEA may also be elevated in those with this form of cancer. People with medullary thyroid cancer can also have a CEA blood test to check for genetic mutations linked to other conditions, like MEN-2.
What Imaging Tests Are Used For Thyroid Diagnosis?
A Thyroid Ultrasound (USG) of the neck can be used to gain information about a thyroid nodule without exposing it to any radiation.
USG results that suggest a nodule is cancerous include:
- a dark appearance (called a hypoechoic nodule)
- small calcium deposits (microcalcifications)
- more blood vessels than normal (hypervascularity)
- irregular borders
To confirm the diagnosis of a thyroid cancer, a thyroid biopsy is used.
What Is A Thyroid Biopsy?
A thyroid biopsy involves collecting a small sample of cells so they can be looked at under a microscope for signs of cancers. A small, thin needle placed within a thyroid nodule can draw up the needed cells.
This is called a Fine Needle Aspiration, and can usually be done in a typical exam room with local anesthesia (medicine that numbs the injection area but doesn’t put you to sleep). An ultrasound may be used to help guide the needle into the nodule.
The FNA may give one of four results:
This means that not enough cells were removed to make a diagnosis. Even in the best of hands, this happens 5 to 10% of the time. Typically the FNA will be repeated.
Benign Thyroid Nodule:
This means that there is a 97% chance that the thyroid nodule is not cancer. In most cases, patients with a benign biopsy are watched with an USG and physical exam 6 months later, and then at regularly scheduled times.
Malignant Thyroid Nodule:
This means that there is a 97% chance that the thyroid nodule is cancer (usually a papillary thyroid cancer). Sometimes the results say that the thyroid nodule is "suspicious for thyroid cancer" which means that there is an 80 to 90% chance of cancer.
This means that the cells do not look normal, but they are not clearly cancer cells. There is a 15 to 20% chance of having thyroid cancer with an indeterminate biopsy.
What If The Thyroid Biopsy Does Not Give A Clear Diagnosis?
If there is still uncertainty after the biopsy, the next step may be surgery to get better access to the thyroid and remove a larger section.
Surgery is often necessary to diagnose follicular thyroid cancer and Hurthle cell carcinoma.
Are There Any Tests Done After The Diagnosis Is Made?
After a diagnosis of thyroid cancer has been made, a CT scan may be used to see if the disease has spread to other parts of the body (particularly in cases of anaplastic thyroid cancer).
If a diagnosis of thyroid lymphoma is made, a total body PET scan may be done to look for lymphoma elsewhere in the body in order to stage the patient.
Thyroid cancer can be grouped into different stages, based on their size, their spread, and the involvement of nearby lymph nodes. These stages can help determine treatment options and likely outcomes.
Many cancers are staged using the TNM system. “T” stands for the size of the tumor, “N” describes lymph node spread, and “M” describes any spread to other organs (called metastases.)
Each of the TNM variables can be further broken down like this:
T: Tumor size (in cm)
- T2: 2-4 cm
- T3: > 4 cm
- T4: tumor grows outside of the thyroid
- T4a: grows into nearby structures
- T4b: grows in spine or nearby large blood vessels
N: Lymph Nodes
- NX: regional lymph nodes can't be assessed
- N0: no involved regional lymph nodes
- N1: involved regional lymph nodes
- N1a: involved central neck lymph nodes
- N1b: involved lateral neck or mediastinal (chest) lymph nodes
- M0: no distant metastases
- M1: distant metastes (usually to the lungs, the liver, or bones)
Based on these three categories, the cancer is assigned a Stage of 1, 2, 3 or 4. Stage 1 is the least advanced form of cancer, and Stage 4 is the most advanced.
All anaplastic thyroid cancers are considered Stage 4.
If you are dealing with a thyroid issue, our team at the Columbia Thyroid Center is here to help. Call (212) 305-0444 or request an appointment online.