Diagnosis

The diagnosis of anaplastic thyroid cancer (ATC) can be difficult. One of the most important considerations in the work up and management of a patient with a rapidly enlarging thyroid mass is the speed at which this evaluation is performed. In most cases of thyroid nodule evaluation, the patient and the clinician can proceed at a more relaxed pace. However, if there is a suspicion of ATC, it is imperative that the workup be conducted in rapid fashion, over the course of hours and days.  

The standard diagnostic approaches for thyroid cancer are as follows: physical examination, imaging, blood tests, and a needle biopsy. Anaplastic thyroid cancer can be more challenging to diagnose than other forms of thyroid cancer. Often, additional testing or open biopsies will be required in order to confirm a diagnosis. In contrast to other types of thyroid malignancies, ATC requires a thorough physical exam and imaging studies in order to achieve diagnosis. Early identification of the extent of disease will help doctors determine the best treatment course. 

Physical Exam

To start, a physician will feel (“palpate”) the neck. Anaplastic thyroid cancers tend to be very large and hard. Due to the invasive nature of ATC, the movement of the vocal cords, the opening of the airway, and the patient’s ability to swallow should all be examined in the office as part of the physical exam. Specialized flexible fiberoptic scopes or modified barium swallow tests may be used as part of this evaluation.  This is often done in concert with a speech and swallowing therapist. 

Imaging

Imaging scans, also known as radiologic studies, provide the doctor with a view of the inside of the body. Imaging of the neck will be required to determine the size and location of a tumor, and is a vital step prior to any treatment decision. As noted above, these studies should be conducted within hours or at the most, days of the initial presentation and the suspicion of ATC is entertained.

For thyroid cancer in general, the gold standard initial imaging test is an ultrasound. Ultrasounds are always used to evaluate thyroid nodules, and often lymph nodes in the surrounding neck area. 

However, when anaplastic thyroid cancer is suspected (or confirmed by biopsy), the doctor will likely gain a more complete view of the tumor and surrounding neck anatomy by ordering a CT or MRI scan. These scans will help determine whether the cancer is surgically resectable and whether surrounding structures are invaded. A full-body scan such as a PET/CT will also be performed to determine if any cancer has spread to other parts of the body, which is more common in anaplastic thyroid cancer than in other types. Read more about thyroid ultrasounds.

Blood Tests

There are a number of blood tests that are used to measure thyroid function. These include thyroid hormone, thyroid stimulating hormone, thyroglobulin, and antibodies. To learn more about these blood tests, click here. The results of these tests can help doctors classify a thyroid nodule and decide on the next steps in the diagnostic process. However, given that ATC is almost always extremely aggressive, doctors often skip these tests and proceed directly to biopsy, imaging and molecular testing if a nodule presents with aggressive behavior such as rapid growth or restriction of breathing or eating, 

Biopsy

A biopsy is the removal of a small piece of tissue to examine under a microscope to see if it is cancerous. The best way to perform a biopsy in the thyroid gland is a fine needle aspiration (FNA) biopsy. 

While a diagnosis of ATC can often be obtained with an FNA biopsy, sometimes the diagnosis remains uncertain, and either a core-needle biopsy or an open incisional biopsy performed in the operating room will be needed in order to sample enough tissue to make a final diagnosis. Read more about biopsies.

The results of thyroid nodule FNA biopsies are reported using the Bethesda System, which is a 1-6 scale used to predict how likely it is that the biopsied nodule is cancerous. It is important to know that a doctor may not be completely sure about the pathology for the nodule until it has been surgically removed and examined under the microscope. Keep in mind that the Bethesda System is different from cancer staging.

Unlike other kinds of thyroid cancer, anaplastic cancers grow rapidly enough for changes in size to be noticed on a day-to-day basis. If the biopsy results are positive, or if there is clinical suspicion of anaplastic thyroid cancer, treatment should not be delayed. Read more in the treatment section.

One of the main goals of the biopsy is to obtain a sufficient sample to assess for the presence of biomarkers that can help differentiate ATC from other rapidly growing tumors of the head and neck, such as lymphoma, squamous cell carcinoma of the larynx, and sarcoma.

If the diagnosis of ATC is established, doctors will then perform genetic tests to determine if the cancer expresses the BRAF V600E mutation. The presence of this mutation will be very important in deciding whether the patient is a candidate for specific targeted therapies. Learn more about genetic and molecular testing for thyroid cancer.