Follicular thyroid cancer – Diagnostics – Overview of Information and Clinical Research

Follicular thyroid cancer is a type of cancer that develops in the thyroid gland, a small butterfly-shaped organ in your neck that produces hormones regulating your metabolism. While it’s the second most common type of thyroid cancer, accounting for about 10 to 15 percent of all thyroid cancers, it is highly treatable and often curable, especially when detected early. Understanding how doctors diagnose this condition can help you know what to expect and when to seek medical care.

Introduction: Who Should Undergo Diagnostics and When to Seek Them

Many people with follicular thyroid cancer don’t notice any symptoms in the early stages, which makes regular checkups important. However, if you discover a lump or swelling in your neck, this is a key reason to see your doctor. The lump, called a thyroid nodule, is an abnormal growth of cells in the thyroid gland. Not all thyroid nodules are cancerous, but they need to be checked carefully. In fact, thyroid nodules are quite common, but only a small number turn out to be cancer.^[1]

You should seek medical attention if you experience other warning signs such as pain in your neck, jaw, or ears, changes in your voice or hoarseness, difficulty swallowing, trouble breathing, or swollen lymph nodes in your neck. These symptoms might be caused by the thyroid cancer growing or pressing on nearby structures.^[1]^[4]

It’s important to know that many of these symptoms can also be caused by non-cancerous conditions affecting the thyroid, such as inflammation. This is why proper diagnostic testing is essential. Early detection increases the chances that treatment will work well and that the cancer can be cured completely.^[4]

Anyone can develop follicular thyroid cancer, but it occurs more often in older adults, particularly women. Women are affected about three times more often than men, with the highest number of cases appearing in people between the ages of 40 and 60.^[2]^[3] If you have a family history of thyroid cancer, have been exposed to significant amounts of radiation to your head, neck, or chest area, or live in an area with low iodine in the diet, you may be at higher risk and should be more alert to symptoms.^[15]

⚠️ Important

Sometimes a doctor may find a thyroid nodule during a routine physical exam, even when you have no symptoms. This is one reason why regular medical checkups are valuable. If your doctor finds a nodule, they will likely recommend further testing to determine whether it needs treatment, even if you feel completely fine.

Diagnostic Methods

Diagnosing follicular thyroid cancer involves several steps because it can be challenging to tell the difference between a benign (non-cancerous) thyroid growth and a cancerous one just by looking at cells under a microscope. Your doctor will use a combination of approaches to get a complete picture.^[7]

Physical Examination

The first step is usually a physical exam. Your doctor will carefully feel your neck to check for any lumps, nodules, or enlargement of the thyroid gland. They will also check the lymph nodes in your neck to see if any are swollen, which could suggest that cancer has spread. During this exam, your doctor will also ask about your medical history, including whether anyone in your family has had thyroid cancer or whether you’ve been exposed to radiation.^[4]^[9]

Blood Tests

Blood tests are used to measure the levels of thyroid hormones and other substances in your blood. These tests check how well your thyroid is functioning. The hormones measured include TSH (thyroid-stimulating hormone) and T4 (thyroxine). Your doctor might also check for antithyroid antibodies to rule out other thyroid conditions. It’s important to understand that blood tests alone cannot diagnose thyroid cancer, but they help your doctor understand the overall health of your thyroid gland.^[1]^[4]

Ultrasound

An ultrasound is a key imaging test that uses sound waves to create detailed pictures of your thyroid gland. This test is painless and does not use radiation. The ultrasound helps your doctor see the size, shape, and characteristics of any nodules in your thyroid. It can show whether a nodule is solid or filled with fluid, and whether it has features that are more commonly seen in cancerous growths. The ultrasound is also used to check the lymph nodes in your neck to see if cancer may have spread.^[1]^[17]

Fine-Needle Aspiration Biopsy

When a nodule is found, a fine-needle aspiration biopsy, often called FNA, is usually performed. During this procedure, a very thin needle is inserted into the thyroid nodule to remove a small sample of cells. The doctor often uses ultrasound guidance to make sure the needle goes into the right spot. The cell sample is then examined under a microscope by a specialist called a pathologist.^[4]^[17]

However, there is an important limitation with fine-needle aspiration when it comes to follicular thyroid cancer. The biopsy can show that the cells are follicular cells, but it cannot always tell whether they are cancerous or benign. This is because the diagnosis of follicular cancer requires seeing whether the cancer cells have invaded the capsule (the outer covering) of the nodule or have entered blood vessels. These features can only be seen when a larger piece of tissue is examined after surgery.^[7]^[11]

If the FNA results are unclear or show a follicular neoplasm (which means “new growth” but doesn’t specify if it’s cancer or not), your doctor will likely recommend surgery to remove at least part of the thyroid so the tissue can be fully examined.^[11]

Core Needle Biopsy

If the fine-needle aspiration biopsy doesn’t provide clear answers, your doctor might perform a core needle biopsy. This uses a slightly larger needle to remove a bigger sample of tissue, which can sometimes provide more information.^[4]

Imaging Tests

Additional imaging tests may be recommended to get more detailed pictures of your thyroid and to check if cancer has spread to other parts of your body. These tests can include a CT scan (computed tomography) or MRI (magnetic resonance imaging), which create detailed cross-sectional images of your body. These scans help doctors see the exact location and size of the cancer and whether it has spread to nearby structures or distant organs such as the lungs or bones.^[4]

Follicular thyroid cancer is more likely than some other types of thyroid cancer to spread through the bloodstream to distant parts of the body, particularly the lungs and bones. Imaging tests help doctors identify this spread, which is called metastasis.^[2]^[6]

The Role of Surgery in Diagnosis

Because it is difficult to confirm follicular thyroid cancer before surgery, many patients undergo a surgical procedure called a lobectomy (removal of one lobe of the thyroid) to get a definitive diagnosis. During this surgery, the removed tissue is sent to a pathologist, who examines it carefully to look for signs of capsular invasion or vascular invasion. These are the hallmark features that distinguish follicular cancer from a benign follicular adenoma.^[7]^[12]

If the pathologist confirms that the nodule is cancerous, your doctor may recommend a second surgery called a completion thyroidectomy, which removes the remaining part of your thyroid. In some cases, if the cancer is suspected to be more advanced, the surgeon may perform a total thyroidectomy (removal of the entire thyroid gland) during the first surgery.^[8]^[12]

⚠️ Important

You may be told you have a “follicular lesion” or “follicular neoplasm” based on your biopsy, but this does not necessarily mean you have cancer. The only way to know for sure is through surgery and examination of the tissue. This can feel frustrating, but it’s the most reliable way to get an accurate diagnosis and ensure you receive the right treatment.

Diagnostics for Clinical Trial Qualification

If you are considering participating in a clinical trial for follicular thyroid cancer, you will need to undergo specific tests and evaluations. Clinical trials are research studies that test new treatments or approaches, and they have strict criteria for who can participate. Understanding these requirements can help you know what to expect if you explore this option.

Confirmation of Diagnosis

Before you can enroll in a clinical trial, the diagnosis of follicular thyroid cancer must be confirmed through histological examination. This means a pathologist has examined tissue from your thyroid under a microscope and identified the cancer cells, including confirming features like capsular or vascular invasion. The pathology report will specify the type of thyroid cancer you have, which is essential because clinical trials often focus on specific cancer types.^[3]

Staging and Extent of Disease

Clinical trials often require detailed information about the stage of your cancer, which describes how large the tumor is and whether it has spread. To determine the stage, you may need imaging tests such as ultrasound, CT scans, MRI, or other scans to assess the size of the primary tumor and check for spread to lymph nodes or distant organs like the lungs or bones.^[6]

Doctors use a staging system to classify thyroid cancer. For follicular thyroid cancer, important factors include the size of the tumor, whether it has grown beyond the thyroid gland, whether lymph nodes are involved, and whether there is distant metastasis. Your age also plays a role in staging, as patients over 55 years old may have different risk categories than younger patients.^[2]

Blood Tests and Tumor Markers

Clinical trials may require specific blood tests to check your overall health and to measure tumor markers. For follicular thyroid cancer, a substance called thyroglobulin (Tg) can be used as a tumor marker. Thyroglobulin is a protein produced by thyroid cells, and measuring its level in your blood can help doctors monitor the cancer and check whether it has come back after treatment. Before joining a trial, your thyroglobulin level might be measured as a baseline.^[7]

Other blood tests will check your thyroid function, including TSH and T4 levels, and may also assess your kidney and liver function to ensure you can safely tolerate the treatments being studied in the trial.^[1]

Genetic and Molecular Testing

Some clinical trials focus on specific genetic changes or mutations found in thyroid cancer cells. Approximately half of follicular thyroid cancers have mutations in genes called RAS, and about one-third have a specific genetic rearrangement called PAX8-PPARγ fusion. If you are considering a clinical trial that targets these genetic features, your tumor tissue may be tested to see if it has these mutations.^[3]^[7]

Molecular testing involves analyzing the DNA of your cancer cells to identify specific genetic changes. This information helps match you with the most appropriate clinical trial and can also guide your overall treatment plan.^[3]

Imaging for Trial Enrollment

Many clinical trials require recent imaging studies to confirm the extent of your disease before you can enroll. This may include a comprehensive ultrasound of your neck and thyroid, CT scans of your chest to check for lung metastases, and bone scans or other imaging if there is concern about cancer spreading to your bones. These baseline images are also used later to measure how well the treatment in the trial is working.^[4]^[6]

Performance Status Assessment

Clinical trials often require that participants have a certain level of physical functioning, known as performance status. This is usually assessed using standardized scales that measure your ability to carry out daily activities and take care of yourself. Your doctor will evaluate whether you are well enough to participate in the trial and handle the treatments being studied.^[6]

Additional Evaluations

Depending on the specific clinical trial, you may need other tests or evaluations. These could include heart function tests if the trial involves medications that might affect the heart, or assessments of your overall nutritional status and quality of life. Each clinical trial has its own specific requirements, and the research team will explain what is needed for the study you are considering.^[6]

Participating in a clinical trial can give you access to new treatments that are not yet widely available. However, it’s important to discuss the potential benefits and risks with your doctor and to make sure you understand what the trial involves before deciding to participate.

Prognosis and Survival Rate

Prognosis

The prognosis for people with follicular thyroid cancer is generally very good, especially when the cancer is detected and treated early. Several factors affect how the disease will progress and how well treatment will work. The size of the tumor is one of the most important factors. Tumors smaller than 1 centimeter (about three-eighths of an inch) have an excellent prognosis, while larger tumors may have a slightly higher risk of spreading or coming back after treatment.^[2]

Age is another significant factor. Patients younger than 55 years old tend to have better outcomes than older patients. In younger patients, the cancer usually responds better to treatment, and even if it has spread to lymph nodes or other parts of the body, the long-term survival is still excellent. Patients over 55 years old may have a more aggressive form of the disease, and the cancer may not absorb radioactive iodine as well, which is an important part of treatment.^[2]

Whether the cancer has spread also affects the prognosis. Follicular thyroid cancer is less likely than papillary thyroid cancer to spread to lymph nodes (this happens in only about 8 to 12 percent of cases), but it has a greater tendency to spread through the bloodstream to distant organs like the lungs and bones. This kind of spread, called distant metastasis, makes treatment more challenging, but many patients still have good outcomes with appropriate care.^[2]^[6]

A unique characteristic of follicular thyroid cancer is vascular invasion, which means cancer cells have entered blood vessels. The degree of vascular invasion is directly related to prognosis. When vascular invasion is extensive, there is a higher risk that the cancer will spread to other organs, which can affect long-term survival.^[2]

Overall, follicular thyroid cancer is highly treatable and often curable. Most patients respond well to treatment with surgery and, when needed, radioactive iodine therapy. The chance of the cancer coming back is relatively low, but long-term monitoring is important. With proper treatment and follow-up care, the vast majority of patients with follicular thyroid cancer live long, healthy lives.^[1]^[19]

Survival Rate

The survival rate for follicular thyroid cancer is excellent compared to many other types of cancer. For patients whose cancer has not spread outside the thyroid gland (called localized disease), the five-year survival rate is nearly 100 percent. This means that almost all patients with localized follicular thyroid cancer are alive five years after their diagnosis.^[15]

When the cancer has spread to nearby lymph nodes or tissues in the neck (called regional disease), the five-year survival rate remains very high at about 98 percent. Even when cancer is found in the lymph nodes, most patients do very well with treatment.^[15]

If follicular thyroid cancer has spread to distant parts of the body, such as the lungs or bones (called metastatic disease), the five-year survival rate is 63 percent. While this is lower than for localized or regional disease, it is still considerably better than the survival rates for many other types of cancer that have spread. This reflects the fact that follicular thyroid cancer, even when advanced, often responds to treatment.^[15]

Overall, the five-year survival rate for all people with thyroid cancer, including follicular thyroid cancer, is about 98 percent. Long-term survival rates are also very high, with 95 percent or more of patients surviving 10 years or longer after diagnosis. These statistics demonstrate that thyroid cancer is one of the most survivable types of cancer.^[15]^[19]

It’s important to remember that survival rates are based on large groups of people and cannot predict exactly what will happen in your individual case. Many factors influence your personal prognosis, including your age, the size and characteristics of your tumor, how it responds to treatment, and your overall health. Your doctor can provide more specific information about your own situation based on these factors.^[20]

Statistics from the United Kingdom show similar patterns. For papillary and follicular thyroid cancers combined, more than 85 out of every 100 men and almost 95 out of every 100 women survive for five years or more after diagnosis. Ten-year survival is also excellent, with around 85 out of every 100 people surviving 10 years or more.^[20]

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