What Is Follicular Thyroid Cancer?

Follicular thyroid cancer is the second most common type of thyroid cancer, and occurs most often in women between ages 40 and 60. This type of cancer is usually first discovered through palpation of the neck. Ultrasound images, blood tests, and biopsies are used to try and confirm the diagnosis. Treatment is with surgery to remove all or part of the thyroid. Follicular thyroid cancer that has spread is treated with radioactive iodine therapy.

The thyroid hormones are produced and secreted by the follicular thyroid cells. When these cells become malignant, they grow to form a nodule. Malignant nodules grow fairly slowly, so the prognosis is typically good if caught early. The challenge with this type of cancer is that symptoms are rare and diagnosis is difficult. When symptoms are present, they are usually caused by a large nodule and include such indications as a visible mass, difficulty swallowing, voice problems, and minor neck pain.

Most follicular thyroid cancer is first discovered through palpation during a person’s yearly physical. Once a nodule is felt, blood tests are run to evaluate the thyroid hormone levels and check thyroid function. Synthetic thyroid hormone may be given to normalize the levels based on the blood test. An ultrasound review of the thyroid will also be ordered to check the consistency of the nodule. Based on the ultrasound images and blood test results, the doctor will decide if a biopsy is necessary and if an endocrinologist needs to be seen.

Fine needle biopsy (FNB) and coarse needle biopsy (CNB) are the two types of biopsies used to diagnose follicular thyroid cancer. The accuracy of FNB and CNB to detect cancer is minimal, but it is the only diagnostic tool available besides surgery. If cancer is found, surgery will more than likely be performed. When cancer is not detected but is strongly suspected, another biopsy may be ordered or surgery may be performed to get a better view.

Treatment for follicular thyroid cancer is surgery to remove all or part of the thyroid. The amount of tissue removed will depend on the age of the patient and the size of the nodule. Thyroid tissue is needed to make thyroid hormone, so it is a fine balance between taking enough tissue to get all the cancer and leaving enough tissue to still produce thyroid hormone. If the entire thyroid is removed, the patient will need daily synthetic thyroid hormone therapy for the rest of her life.

Follicular thyroid cancer will sometimes metastasize or spread through the blood vessels to the lungs and bones. Metastasized, follicular thyroid cancer is treated with radioactive iodine. Thyroid cells are the only cells that take up iodine for use in the production of thyroid hormones. To destroy metastasized follicular cancer cells, the patient will be given iodine tagged with the toxic radioactive isotope iodine-131. This isotope will be absorbed by and destroy all the thyroid follicular cells around the body, making a precisely targeted form of chemotherapy.