What is Follicular Thyroid Cancer?
The thyroid is a type of gland located in your neck just below the voice box. It’s made up of two sections, the right and the left, which are separated by a thin piece of tissue known as an isthmus. The job of the thyroid gland is to create the thyroid hormone, which helps your body carry out different processes related to metabolism.
The thyroid gland is made of small sacs known as follicles, which are the working parts of the gland. These follicles are lined with a layer of cells, which can change shape depending on how active the gland is. In some cases, these cells could grow abnormally, leading to a type of cancer known as follicular malignancy.
Thyroid cancer is one of the most common types of tumours affecting the endocrine system, which is the group of glands that produce hormones. Thyroid cancers can be classified as differentiated or undifferentiated. Differentiated cancers include papillary and follicular thyroid carcinoma, and undifferentiated types include medullary thyroid cancer and anaplastic cancer. The most common type is papillary thyroid cancer.
Follicular thyroid cancer is the second most common type and accounts for 10 to 15% of all thyroid cancer cases. The undifferentiated types are much less common compared to the differentiated types.
About half of cases with follicular carcinoma, a specific type of thyroid cancer, have a certain genetic mutation known as RAS point mutations. Around one-third may have PAX-PPAR-gamma rearrangements, another type of genetic change, and only 3% have both. Follicular thyroid cancer originates from specific thyroid cells and has the ability to invade surrounding tissues and blood vessels.
There’s another condition known as follicular adenoma that’s similar to follicular carcinoma but is benign, meaning it’s not cancerous. It’s also more common than follicular carcinoma, with a ratio estimated to be 5 to 1.
This discussion will focus on follicular thyroid cancer, including its causes, commonness, cell structure, assessment, progression, and possible complications.
What Causes Follicular Thyroid Cancer?
Thyroid cancer can be caused by a variety of factors like exposure to radiation, the amount of iodine you eat, having diabetes or obesity, a condition called Hashimoto thyroiditis, using a type of hormone called estrogen, or even the food you choose to eat. For instance, after the Chornobyl disaster in 1986, a high number of people developed thyroid cancer due to radiation exposure.
Your thyroid, located in your neck, is especially sensitive to radiation, and this is particularly true for young people. Studies have observed that the risk of getting cancer from radiation exposure can last for over 50 years. Beyond disasters like nuclear explosions, you can also be exposed to radiation through medical procedures like X-rays and CT scans. The more such scans you have, the higher your chances of developing thyroid cancer might be.
There’s ongoing debate about whether too much or too little iodine might lead to thyroid cancer. Some studies argue that a high intake of iodine can increase the risk of thyroid cancer. But others suggest that not getting enough iodine might lead to a specific type of this cancer.
Conditions like diabetes and obesity have also been linked to a higher risk of thyroid cancer. Similarly, a condition called Hashimoto thyroiditis, which causes inflammation of the thyroid, has been linked to an increase in thyroid cancer. This might be due to the fact that it leads to more pro-inflammatory cytokines (proteins that help send signals in your body) and oxidative stress (an imbalance of antioxidants and damaging molecules called free radicals in your body).
Diet can also play a significant role in the chances of developing thyroid cancer. Certain types of food such as cabbage, broccoli, cauliflower, chicken, pork, and poultry have been associated with a higher incidence of thyroid cancer. On the other hand, foods like persimmons and tangerines have been linked with a lower incidence of this condition. Furthermore, high iodine content in multivitamins gotten from excessive use, or from foods that contain a high amount of nitrate or nitrite, might increase the chance of developing thyroid cancer.
Lastly, some jobs have been linked with a higher risk of thyroid cancer. These include jobs that expose you to radiation or pesticides, or jobs in the textile industry.
Risk Factors and Frequency for Follicular Thyroid Cancer
Thyroid cancer is the ninth most common type of cancer and makes up almost 4% of all new cancer diagnoses in the U.S. In 2017, it was estimated that there would be 56,780 new cases of thyroid cancer, and it is more common in women than men. The second most common type of thyroid cancer is follicular thyroid cancer, which accounts for between 4% to 39% of all thyroid cancer cases. This type is more frequently found in older women, with three times as many women being diagnosed as men, and is often diagnosed around the age of 60.
- Thyroid cancer is the ninth most common cancer.
- It makes up about 4% of all new cancer cases in the U.S.
- In 2017, the number of new cases was projected to be 56,780.
- Thyroid cancer is more common in women than men.
- Follicular thyroid cancer is the second most common type of thyroid cancer.
- This type of cancer represents between 4% and 39% of all thyroid cancer cases.
- Follicular thyroid cancer more often affects older women, typically around the age of 60.
- In areas with sufficient iodine, the incidence of follicular thyroid cancer is around 10%.
- In areas with iodine deficiency, the incidence can rise to between 25 and 40%.
- In the U.S., however, the incidence of follicular thyroid cancer has declined thanks to the elimination of iodine deficiency.
Signs and Symptoms of Follicular Thyroid Cancer
People with thyroid cancer may have a larger thyroid gland because of a lump in one or both parts of the gland. Sometimes, they might show symptoms like those seen in hypothyroidism or hyperthyroidism. However, most of the time, they don’t have any symptoms.
Testing for Follicular Thyroid Cancer
To diagnose primary thyroid cancer, doctors often use ultrasound imaging or a method guided by ultrasound called fine needle aspiration or core biopsy. The ultrasound of primary thyroid cancer commonly shows solid areas that send back fewer echoes (hypoechoic nodules) with small specks of calcium (micro-calcification), unclear edges, and blood vessel patterns inside the nodule rather than around it.
CT and MRI scans are helpful to check how far the tumor has spread outside the thyroid but they are not routinely used for evaluating the thyroid nodule itself. After taking samples from fine needle aspiration or core biopsy, these samples are then checked under a microscope for confirmation.
Follicular thyroid carcinoma, a type of thyroid cancer, is diagnosed based on confirmation from a pathologist that the cell samples show follicular cells but without the abnormal characteristics found in another type of thyroid cancer called papillary thyroid cancer. These abnormal characteristics include invasion of the tumor into the capsule (a layer of fibrous tissue surrounding the thyroid or the tumor) or into blood vessels.
If the cancer is invasive (it can spread) and mainly consists of follicles (small sacs in the thyroid that produce thyroid hormones), it is termed as follicular thyroid carcinoma. However, different pathologists might interpret the cell structures differently, which can sometimes lead to disagreement in the classification of follicular thyroid carcinoma. To help assess the condition, scans such as the CT scan can be used to identify if the follicular thyroid carcinoma has spread to other parts of the body (metastatic).
Treatment Options for Follicular Thyroid Cancer
When it comes to follicular thyroid carcinoma, a type of thyroid cancer, the approach for treatment and management depends on how advanced the cancer is when it’s detected.
If the cancer has minimally invasive characteristics – meaning it’s not yet deeply rooted – doctors typically perform a thyroid lobectomy and isthmectomy. This means they’ll remove a lobe of the thyroid and the isthmus, a small bridge of tissue that connects the two thyroid lobes.
But if the cancer is invasive – meaning it has spread to deeper tissues – more comprehensive steps are required. Total thyroidectomy is usually recommended, which is a surgical procedure to remove all of the thyroid gland. This is often followed by radioiodine ablation, which uses radioactive iodine to destroy any remaining thyroid tissue or cancer cells.
Thyrotropin suppressing medications are also commonly used. These are drugs that lower the levels of thyrotropin, a hormone that stimulates the thyroid gland, to help control the growth and division of thyroid cancer cells.
Research has shown a higher chance of the cancer coming back for those who did not undergo radioiodine ablation. Therefore, the standard treatment often includes total thyroidectomy followed by radioiodine radiation.
For those patients where cancer has spread to the bones and soft tissues – known as metastasis – chemotherapy or radiotherapy, or both could be used after the total thyroidectomy. There are different types of chemotherapy that can help control tumor growth and improve progression-free survival, which is the length of time during and after treatment that the patient lives without the disease getting worse. Among these are tyrosine kinase inhibitors like sorafenib, lenvatinib, vandetanib, and cabozantinib.
There are also newer treatment agents that are being tested and have shown promising responses in some patients. To monitor for any recurrence of cancer, doctors will measure thyroglobulin levels. Thyroglobulin is a protein produced by the thyroid gland, and its levels can rise if thyroid cancer comes back.
What else can Follicular Thyroid Cancer be?
When trying to identify a case of follicular thyroid carcinoma, doctors have to consider a few other conditions that could look similar. These include:
- A distinct type of papillary thyroid carcinoma known as the follicular variant
- Typical papillary thyroid carcinoma
- A condition called noninvasive follicular thyroid neoplasm with papillary-like nuclear features, or NIFTP for short
- Follicular adenoma
There’s some disagreement in the medical field about how to correctly identify follicular thyroid carcinoma. This happens because different pathologists (the doctors who examine the cells) might contradict each other. The reasons behind this disagreement mainly revolve around the extent of unusual cell growth and invasion into surrounding barriers or blood vessels.
NIFTP is a new category that’s been added for doctors describing cases of thyroid cancer. It’s been recently recognized as a harmless condition, so it’s suggested to treat NIFTP as benign. Kit of research is being done to create specific guidelines for using ultrasound scans to more accurately distinguish between malignant (harmful) and benign (harmless) abnormalities.
What to expect with Follicular Thyroid Cancer
Despite a rise in the number of people diagnosed with thyroid cancer, the death rate from it has remained constant. Of all the various types of cancers in the US, thyroid cancer is associated with one of the lowest death rates. In 2017, it was estimated that approximately 2,010 people died from thyroid cancer, significantly lower compared to over 150,000 deaths from lung cancer.
Follicular thyroid cancer is typically a more serious form than papillary thyroid cancer. This is because it has a higher chance of spreading to other parts of the body and patients often have a more advanced stage of the disease when they are first diagnosed.
Despite this, it’s important to note that follicular thyroid cancers are less likely to spread to the lymph nodes, with estimates suggesting this happens in less than 10% of cases. Some research also suggests that when taking into account factors like age and sex, there might not actually be a significant difference in the prognosis (the likely course of the disease) between follicular and papillary thyroid cancer.
When it comes to the survival rate for follicular thyroid cancer, much depends on the invasiveness of the cancer. Patients with minimally invasive cancers have a 10-year survival rate of around 98%, while for those with more invasive forms of follicular cancer, this figure stands at 80%. According to some studies, the survival rate can vary between 46% to 97%, depending mainly on whether the cancer has invaded the capsule (a protective barrier around the thyroid) or the blood vessels.
The death rate for follicular thyroid cancer ranges from 5 to 15%, and those whose cancer has invaded the capsule generally have a poorer prognosis than those without this invasion.
Possible Complications When Diagnosed with Follicular Thyroid Cancer
The most serious concern with follicular thyroid cancer is the spread of the disease to other parts of the body, also known as metastasis. According to research, this typically occurs in the bones, lungs, and lymph nodes. One study found that among their patients, 42% had the disease spread to their bones, 33% to their lungs, and 8% to their lymph nodes. Overall, it’s estimated that between 6 to 20% of people with this type of thyroid cancer experience such disease spread.
Surgery to treat the cancer can also lead to complications. Since the thyroid gland is close to the laryngeal nerves involved in voice production, they could accidentally be harmed during surgery. This could make the patient’s voice hoarse. Some patients also reported developing a blood clot or keloid (raised, reddish nodules that form at the site of healed skin injuries) after having the surgery.
Moreover, because the treatment involves completely removing the thyroid, a condition called hypothyroidism (underactive thyroid) will develop. This means patients will need to take medication to replace the hormone thyroxine, which the thyroid ordinarily makes.
Possible complications:
- Metastasis (spread of cancer to bone, lungs, or lymph nodes)
- Hoarseness from damage to laryngeal nerves during surgery
- Hematoma (blood clot) or keloid (raised scar) formation after surgery
- Hypothyroidism requiring thyroxine replacement medication
Preventing Follicular Thyroid Cancer
Thyroid cancer generally has a better prognosis or outcome compared to other types of cancer. However, hearing the word ‘cancer’ can still understandably worry many patients. This can lead to some patients choosing to have their thyroid surgically removed, even if they have a type of thyroid cancer called non-invasive follicular thyroid cancer, which grows slowly and can often just be monitored. It’s extremely important for patients and their doctors to discuss and decide the best treatment option together.
Being well-informed about their condition can help patients make better decisions about their health. This includes understanding the nature of their specific type of cancer, the various treatment options available and the potential benefits and risks associated with each method. When a patient is knowledgeable about their health, they can feel more confident and comfortable in their treatment decisions.
