Thyroid follicular adenoma is a common benign tumor of the thyroid gland. They can be detected as a hard nodule in the thyroid gland or an enlargement of the existing nodule or as thyroiditis. While very few thyroid nodules can be palpated, the majority are discovered incidentally by ultrasonography. These nodules are usually asymptomatic.
Follicular thyroid adenomas develop mostly randomly. It is almost the same as the causes of all thyroid diseases in that its causes include iodine deficiency, genetic predisposition, and a history of radiation exposure. In fact, iodine-131 radiation exposure further increases the risk of malignancy. Environmental radiation exposure is also an important risk factor for both thyroid follicular adenoma and all other thyroid diseases.
Thyroid follicular adenoma can range in size from a few millimeters to 10-15 cm. It is usually encapsulated and hard mass. It does not invade surrounding tissues. Malignancy is considered in structures that overflow the capsule and extend outward with their vessels.
Patients with thyroid follicular adenoma may present to the physician with a normal thyroid nodule or signs of thyroiditis. Thyroid hormone abnormalities are not seen in almost all follicular adenomas. Hyperthyroidism can be seen in up to 1% of patients. Swelling in the neck of the patients and the history of thyroid drug use indicate a condition that requires detailed evaluation. Having familial thyroid diseases requires careful investigation. Patients usually present with complaints of swelling, hoarseness, cough, difficulty in swallowing or shortness of breath that impair the aesthetic appearance.
Diagnosis of thyroid follicular adenoma:
Detailed patient history, physical examination, serum TSH and thyroid hormones testing followed by an ultrasound are standard practice in the diagnosis of thyroid follicular adenoma. Since nodules larger than 1 cm detected by ultrasonography can transform into malignant forms, detailed evaluation is needed in diagnosis and treatment. Fine-needle aspiration biopsy can be performed under ultrasound guidance to help support the diagnosis. Fine needle aspiration cytology cannot differentiate between follicular adenoma or carcinoma. Definitive diagnosis is made by tissue biopsy specimen.
In case of detection of thyroid nodules larger than 1 cm, serum TSH evaluation is performed. If the TSH level is low, a radioactive screening test may be required. Radionuclide screening is not recommended if the TSH value is normal or high.
Computed tomography or magnetic resonance imaging can be performed in rare cases such as invasion or pressure on surrounding tissues, spread to the mediastinum, or suspected tracheal involvement with recurrent disease.
Definitive diagnosis of follicular adenoma is made by histological examination after excluding capsule and vessel invasion with standard noduleectomy or thyroidectomy.
Treatment of thyroid follicular adenoma:
The treatment of thyroid follicular adenoma is surgery. Thyroid suppression therapy with levothyroxine may be required in eligible patients prior to surgical treatment. In cases with low serum TSH value, drug therapy may be required, as a toxic form may develop.
With surgical treatment, pressure-compressive symptoms such as dyspnea, dysphagia and hoarseness disappear in the patient. If there is also a toxic follicular adenoma, the risks for possible development of thyrotoxicosis are removed. Although there are post-surgical complications, these are mostly controllable conditions.