Follicular thyroid cancer is a form of thyroid cancer characterized by the follicular structure of the tumor. It is manifested by the presence of a tumor-like formation in the thyroid gland, pain, voice changes, difficulty breathing and swallowing in combination with general symptoms of cancer. Rarely affects regional lymph nodes. It can metastasize to the lungs, bones, brain, skin and other organs. It is diagnosed taking into account clinical signs, examination data, laryngoscopy, ultrasound, CT, MRI, puncture biopsy and other diagnostic procedures. Treatment – hemithyroidectomy or thyroidectomy, radioactive iodine, replacement therapy.
Follicular thyroid cancer is the second most common form of thyroid cancer after papillary cancer. It makes up 14-15% of the total number of thyroid cancers. It usually develops after the age of 40, but it can also be diagnosed in children. Women suffer three times more often than men. Follicular thyroid cancer is considered more aggressive than papillary. Rarely affects lymph nodes, can give distant metastases. At the initial stages, it is considered as prognostically favorable, the five-year survival rate of patients with local forms of neoplasia is approaching 100%. With invasion into the surrounding tissues and the occurrence of metastases, the prognosis worsens. The treatment is carried out by specialists in the field of oncology and endocrinology.
It has been established that usually oncological lesion of this organ occurs against the background of an already existing goiter. Along with goiter, factors that increase the risk of developing follicular cancer include chronic inflammatory processes in the thyroid gland, thyroid adenoma and some hereditary diseases. There is a connection with inflammatory processes and tumors of the female reproductive system. The probability of follicular thyroid cancer increases during periods of hormonal restructuring of the body (during gestation, during menopause). The researchers point out that follicular cancer relatively rarely manifests after receiving an increased dose of ionizing radiation.
In appearance, follicular thyroid cancer resembles adenoma. Microscopic examination of highly differentiated neoplasms reveals follicles similar to normal thyroid follicles. The lining cells are polymorphic, with hyperchromic nuclei. Moderately differentiated tumors are characterized by clusters of cells in the node tissue and inside the follicles. B-cell cancer consists of small follicles and cell clusters.
In accordance with the TNM classification, the following stages of follicular thyroid cancer are distinguished:
- T1 – a neoplasm with a diameter of no more than 2 cm is detected. Sometimes there is a T1a node with a size of no more than 1 cm and a T1b node with a size of 1-2 cm .
- T2 – neoplasia with a diameter of 2-4 cm is detected .
- T3 – a node with a diameter of more than 4 cm is detected, which does not extend beyond the organ.
- T4 – follicular thyroid cancer affects neighboring organs. T4a – invasion of the larynx, trachea and laryngeal nerve is determined. T4b – the tumor sprouts the carotid artery and fascia of the neck.
In the absence of lymphogenic metastasis, the marking N0 is used, in the absence of distant metastasis – M0. Lymphogenic and hematogenous metastases, respectively, are designated N1 and M1.
There are no symptoms in the initial stages. Subsequently, a rounded dense knot appears on the front surface of the neck in the thyroid gland area. In the presence of goiter, the node may go unnoticed or be interpreted as a progression of primary pathology. With the further growth of follicular thyroid cancer, there are pains in the projection of the organ, shortness of breath and difficulty swallowing. When the laryngeal nerve is involved, hoarseness and voice changes are detected. Unlike papillary cancer, enlarged lymph nodes on the neck are found quite rarely. Thyroid function is usually not impaired.
Follicular thyroid cancer is characterized by relatively slow growth. The germination of nearby organs and the formation of distant metastases are accompanied by a deterioration in the general condition of patients. Pronounced weakness, apathy, fatigue, mood instability, loss of appetite, weight loss, anemia, pallor of the skin and hyperthermia are revealed. Distant metastases most often affect the lungs and bones, less often the liver, skin and brain.
With metastasis of follicular thyroid cancer to the lungs, an asymptomatic course may be observed (in case of peripheral lesions) or the appearance of a cough with an admixture of blood in sputum. Bone metastases are manifested by pain and pathological fractures. With metastases in the liver, there are pains in the right hypochondrium and hepatomegaly, jaundice is possible. Manifestations of metastases in the brain are determined by the localization of secondary foci. Headaches and neurological symptoms are characteristic.
Usually, with existing complaints, patients primarily turn to an endocrinologist. The doctor directs patients to consult an oncologist and an otolaryngologist. If signs characteristic of follicular thyroid cancer are detected, further examination is carried out by an oncologist. The examination plan includes ultrasound, CT and MRI of the thyroid gland. The listed procedures make it possible to clarify the prevalence and structure of the node, as well as the presence or absence of clear boundaries of the neoplasm.
The patient is prescribed tests to determine the level of thyroid hormones. Laryngoscopy is performed to assess the degree of laryngeal involvement. The final diagnosis of follicular thyroid cancer is established taking into account the results of a histological examination of a tissue sample obtained during a fine needle biopsy. To detect metastases, skeletal scintigraphy, ultrasound and CT of the liver, chest X-ray examination, brain MRI and other diagnostic procedures are performed. The disease is differentiated from other forms of cancer and thyroid diseases of a non-tumor nature.
Treatment and prognosis
The main method of treatment is surgical removal of the tumor. The volume of the operation is determined taking into account the prevalence of the oncological process. Oncologists’ opinions on the required volume of resection for local follicular thyroid cancer differ. Some surgeons believe that a small number of relapses allows for hemithyroidectomy. Others point out that malignant cells are often found in the remaining fraction, and insist on the complete removal of the organ. With large neoplasias, a thyroidectomy is performed.
In the postoperative period, patients with follicular thyroid cancer are prescribed iodine radiopreparations (isotope iodine-131). This technique is also used when involving lymph nodes and neighboring organs, if there are contraindications to surgical intervention in elderly patients and patients with severe somatic pathology. After removal of the thyroid gland, hormone replacement therapy is carried out throughout life. Patients are recommended to be regularly monitored by an endocrinologist oncologist. Chest radiography is prescribed annually.
The prognosis for follicular thyroid cancer is relatively favorable. The average five-year survival rate is about 90%. When the disease is detected at stages 1 and 2, almost 100% of patients survive up to 5 years from the moment of surgery. With common forms of the disease, this indicator decreases. In the group of patients with stage 3 follicular thyroid cancer, the five–year survival rate is 71%, in the group with stage 4 – 50%.