Anaplastic Thyroid Cancer

June 15, 2024 
This page was reviewed under our medical and editorial policy by Sasan Fazeli, M.D., assistant clinical professor in the Department of Diabetes, Endocrinology and Metabolism, and Karen Tsai, M.D., assistant clinical professor in the Department of Diabetes, Endocrinology and Metabolism, City of Hope^® Cancer Center Duarte.

Several types of cancer may affect the thyroid gland, including anaplastic thyroid cancer (ATC). Anaplastic thyroid cancer is very rare, representing 1% to 2% of all thyroid cancer cases.

This guide explores what patients with ATC and their families need to know about the causes and symptoms of this cancer and how it may be treated.

What Is Anaplastic Thyroid Cancer?

Health care providers may refer to ATC as anaplastic thyroid carcinoma or undifferentiated thyroid carcinoma. It’s considered an aggressive cancer that may be difficult to treat.

Most thyroid cancers are considered differentiated cancers. This means that their cells look similar to normal thyroid cells when viewed with a microscope. ATC, on the other hand, is an undifferentiated thyroid cancer. Its cells bear little resemblance to normal thyroid cells.

When these higher-grade, undifferentiated cells divide quickly and grow out of control, a cancerous mass forms in the thyroid, and in time, the cells tend to spread to other areas of the body.

Metastatic Anaplastic Thyroid Cancer

Cancer staging is a method used by doctors to describe the disease extent and burden of a cancer and is essential in guiding treatment and predicting treatment response. It takes into account the size of the primary tumor, whether the cancer has spread to nearby lymph nodes and whether the cancer has metastasized (spread) to other organs in the body.

ATC spreads very quickly. For this reason, all cases of anaplastic thyroid cancer are considered Stage 4, regardless of the tumor size, lymph nodes or spread. ATC is further divided into three substages, described below.

Stage 4A: This tumor has spread to nearby structures in the neck, but not to distant places in the body.

Stage 4B: Tumors have spread beyond nearby structures, but not to distant areas of the body.

Stage 4C: This stage indicates that cancer has metastasized, or spread, to areas in the body far away from the thyroid.

Anaplastic Thyroid Cancer Symptoms

The most common initial symptoms of anaplastic thyroid cancer may include:

• A fast-growing, painful, hard lump in the neck
• Hoarseness
• Trouble swallowing
• Trouble breathing
• Cough
• Vocal cord paralysis
• Neck enlargement

Patients experiencing any of these symptoms should immediately make an appointment with a health care provider to rule out this diagnosis.

What Causes Anaplastic Thyroid Cancer?

Researchers are not sure what causes anaplastic thyroid cancer. They have found that it often begins in thyroid cells that are already affected by another medical condition, such as goiter or another type of thyroid cancer. Many types of cell changes have been found in anaplastic thyroid cancer, which suggests that it may originate in different ways. Multiple genetic alterations in the anaplastic cancerous cells have been seen, which may be an underlying cause in some patients.

Patients who develop ATC tend to be over 60 years old and are more likely to be female, although anyone may be affected by this disease.

Anaplastic Thyroid Cancer Diagnosis

If the care team suspects anaplastic thyroid cancer, they will take the patient in very quickly and order several tests to confirm the diagnosis and determine if it has spread. Tests include those listed below.

Imaging: Different types of imaging scans, such as ultrasound, computed tomography (CT), positron emission tomography-CT (PET-CT) or magnetic resonance imaging (MRI), may be used to determine the size of the tumor and check for signs that it has spread (metastasized).

Fine needle aspiration: This is a type of biopsy in which a very small needle is used to take samples of the tumor. A pathologist examines the tissue samples under a microscope to look for cancer cells and some of the features of those cancer cells. Additional molecular testing of the sample can also be sent to help guide diagnosis and treatment.

Anaplastic Thyroid Cancer Treatment

The most common management and treatment options for ATC are airway protection, surgery, radiation therapy, chemotherapy, targeted therapy and immunotherapy. Depending on the patient’s health, a combination of these options, listed below, may be used.

Airway protection: The first step in managing patients with ATC is evaluating their breathing status. Due to fast-growing ATC tumors, some patients present with breathing difficulties. A procedure to secure the airways by an expert head and neck surgeon is essential in those situations. If the patient has difficulty breathing and is suspected of having ATC, they may be referred to the emergency room to ensure they can breathe appropriately. Patients with swallowing difficulties may require a gastric tube for taking in nutrients.

Surgery: If the cancer has not spread, the patient’s thyroid gland will be removed (in a procedure called a thyroidectomy). If the cancer has already spread, surgery may still be performed to remove as much of the tumor as possible, especially any cancer that may block the patient’s airway (debulking surgery).

Radiation therapy: If the patient’s tumor was completely removed, radiation therapy may be used to help destroy any remaining cancer cells. If the tumor could not be removed, radiation therapy may help stop or slow the tumor’s spread.

Chemotherapy: This treatment uses various medications to attempt to destroy cancer cells throughout the body. These drugs attack rapidly growing cells, like cancer cells, but they may also affect other normal, fast-growing cells in the body.

Targeted therapy: Based on the cancer cells’ gene changes, the care team may use special drugs to target those tumors. For anaplastic thyroid cancer, targeted therapies may help treat the cancer, based on certain genetic changes. Some of these genetic changes and their targeted therapies are as follows:

• BRAF gene mutation: Tafinlar^® (dabrafenib) and Mekinist^® (trametinib)
• RET gene fusion: Retevmo^® (selpercatinib) and Gavreto^® (pralsetinib)
• NTRK gene mutation: Vitrakvi^® (larotrectinib) and Rozlytrek^® (entrectinib)
• MEK gene mutation: Mekinist^® (trametinib)
• MTOR gene mutation: Afinitor^® (everolimus)
• ALK gene fusion: Alecensa^® (alectinib), Xalkori^® (crizotinib)

Immunotherapy: Immunotherapy in the form of infusions is being used in anaplastic thyroid carcinoma patients. Because this disease is commonly an immunogenic type of tumor, immunotherapy has been used in combination with other targeted therapies or for maintenance treatment.

Clinical Trials: ATC is difficult to treat because it can rapidly spread in the body and in the neck. Researchers are working on ways to increase the success of ATC treatments. Patients may be able to participate in clinical trials.

Radioactive iodine is a common treatment for other types of thyroid cancer; however, it is not appropriate for anaplastic thyroid cancer.

Anaplastic Thyroid Cancer Survival Rate

Five-year relative survival rates for ATC are estimates based on the percentage of people with the same type and stage of cancer who were still alive five years after their diagnosis. They are based on the previous outcomes of a large number of people who had the same cancer. So, while they give patients an idea of how successful treatments might be, they cannot predict how any individual patient might do.

According to the American Cancer Society, the five-year relative survival rate for anaplastic thyroid cancer is:

• 39% for cancer that has not spread outside the thyroid
• 11% for cancer that has spread to nearby structures
• 4% for cancer that has spread to distant areas of the body

It’s important for patients and their families to remember that the treatments available for ATC may improve over time. This means that patients diagnosed now may have more successful treatment options than patients treated in the past.