Follicular Thyroid Cancer

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Follicular thyroid cancer (FTC) is the second most common type of thyroid cancer after papillary thyroid cancer. Both of these cancers are considered well-differentiated cancers and are highly curable. However, FTC is more aggressive than papillary thyroid cancer. This is mostly due to the fact that FTC spreads more easily to the vascular system and throughout the body than papillary thyroid cancer.

While exposure to radiation often causes papillary thyroid cancer, it is less likely to cause FTC. It may be related to iodine deficiency. Follicular thyroid cancer tends to occur in people who are between the ages of 40-60, and age factors into prognosis. It also occurs more often in women than in men and more often in whites than in blacks. 

Symptoms

There are very few symptoms of follicular thyroid cancer, especially in the early stages of the disease. The first thing you might notice is a lump in your neck which might move up and down when you swallow. Most of the time these tumors are small and cause no discomfort. However, occasionally, a tumor may become so large that it starts to infringe on surrounding structures in the neck including the airway (trachea) or vocal cords. This can cause the following symptoms:

If the cancer has spread to other parts of the body additional symptoms may occur. For example, if cancer has spread to the bones it may be painful or you may have experienced bone fractures. If it has spread to the lungs you may notice breathing difficulty.

Follicular thyroid cancer accounts for about 15 to 20 percent of all thyroid cancers.

Diagnosis

Blood testing usually involves levels of TSH, thyroxine, triiodothyronine, thyroglobulin, calcium, and calcitonin. Elevated levels may indicate FTC but are also often present in other thyroid conditions.

Once a lump on the thyroid has been detected it usually requires further investigation to lead to a determination of malignancy. This is usually done through medical imaging such as ultrasound or radioiodine imaging. Occasionally PET/CT scans may be used. These tests do not definitively determine if a nodule is cancer or not but can help determine if a nodule is more or less likely to be malignant. Tests like chest X-rays or MRI's are generally only used if metastasis is suspected.

These medical imaging tests may or may not be followed by fine needle aspiration (FNA) of the tumor, a procedure that involves removing cells from the tumor with a needle and studying them under a microscope. Of all the diagnostic tests that can be performed to detect thyroid cancer, FNA is perhaps the most conclusive and accurate.

Treatment

One or more of the following treatments may be used to manage follicular thyroid cancer. Each case is different and your exact treatment will be determined based on the size of your tumor and whether or not it has spread beyond the thyroid.

Total or Partial Thyroidectomy

Surgical removal of the tumor and any affected areas is the first-line treatment for follicular thyroid cancer. There is disagreement among medical professionals on whether the entire thyroid or only the affected lobe of the thyroid should be removed in cases where tumors are only found on one side. Whether you have a full or partial removal of the thyroid gland will depend on your specific circumstances and be between you and your doctor.

If the tumor is small and has not spread surgery may be the only treatment you need. If the cancer has spread to any of the lymph nodes in the neck these will also need to be surgically removed and you may need follow up treatments (such as radioactive iodine).

If your thyroid is completely removed you will need to take oral medication for the remainder of your life to replace the thyroid hormones your body is no longer able to make.

Following a thyroidectomy most people spend the night in the hospital. You can expect to have some pain, a sore throat and hoarseness following surgery.

The parathyroid glands, glands which play an important part in regulating calcium, are in close proximity or sometimes actually located within the thyroid and can go into shock following surgery. If this happens calcium levels can drop. For this reason your calcium levels are closely monitored and you may be given oral or intravenous calcium following a thyroidectomy.

Radioactive Iodine

Some cells within the thyroid readily absorb iodine and when given a toxic form of radioactive iodine (I-131) they will absorb it and be killed. Other cells within the body do not absorb iodine and so this is a very good treatment for certain types of thyroid cancer including follicular thyroid cancer.

The cells better absorb iodine if you have high levels of a hormone called thyroid stimulating hormone (TSH). This is achieved by not started thyroid hormone replacement medication immediately following a total thyroidectomy or by the administration of a medication called Thyrogen. Thyroid cells also absorb I-131 better if you follow a low iodine diet for a period of time before you are given this treatment.

Most people who are given radioactive iodine experience no side effects or mild side effects but this may depend on the dose that you are given and your individual response. Potential side effects can include:

  • Nausea and vomiting
  • Pain and swelling in your neck
  • Dry mouth or eyes
  • A strange taste in your mouth
  • Changes in the way food tastes

After you are given I-131 you can emit some radiation for a period of time. Your body eliminates the radioactive iodine through your body fluids including urine, stool, saliva and sweat. This radiation can damage the thyroid cells of people you live with or spend time with and is especially a danger to small children. You will be given specific instructions on how to minimize this risk to your family and the community and you should follow these instructions carefully.

Miscellaneous Treatment for Follicular Thyroid Cancer

Treatments such as external beam radiation therapy and chemotherapy are seldom used to manage follicular thyroid cancer. These treatments are usually reserved for cases where the cancer has spread throughout the body or has not been responsive to other treatment.

Follow-Up Care

If you had a total thyroidectomy your doctor may choose to keep your TSH levels low by giving you a slightly higher dose of thyroxine (the medication used to replace your thyroid hormones). This is because TSH is a hormone that causes your body to grow new thyroid tissue (even cancerous thyroid tissue). Having a higher level of thyroxine signals your pituitary gland that it doesn't need to make TSH.

Other blood work that is monitored usually includes thyroglobulin levels. Thyroglobulin can be used as a type of tumor marker for thyroid cancer especially after a total thyroidectomy.

Other follow-up care for FTC often includes periodic ultrasounds to look for any new growths or radioiodine scans.

A Word From Verywell

The prognosis for FTC is very good. However, the best outcomes are achieved when cancer is detected and treated early on. Following a diagnosis of FTC it will be very important for you to work closely with your doctor and complete any recommended follow-up care so that recurrence of your condition can be avoided or detected and treated early on.

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Article Sources

  1. Luigi Santacroce, MD. Follicular Thyroid Carcinoma Clinical Presentation. Medscape. Updated July 2018. https://emedicine.medscape.com/article/278488-clinical

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