Thyroid cancer is a malignant nodular formation that develops from the follicular or parafollicular (C-cells) epithelium of the thyroid gland. There are follicular, papillary, medullary, anaplastic cancer and thyroid lymphoma, as well as its metastatic lesions. Clinically, thyroid cancer is manifested by difficulty swallowing, a feeling of compression and sore throat, hoarseness, cough, weight loss, weakness and sweating. Diagnosis is carried out according to ultrasound, MRI and thyroid scintigraphy. However, the main criterion is the detection of cancer cells in the material obtained by a fine needle biopsy of the gland.
ICD 10
C73 Malignant neoplasm of the thyroid gland
Meaning
The incidence of thyroid cancer (TC) is about 1.5% of all malignant tumors of other localizations. Breast cancer is more common in women after 40-60 years (3.5 times more common than in men). After the Chernobyl disaster, the incidence of thyroid cancer has increased significantly, especially among children whose thyroid gland is much more sensitive to the accumulation of radioactive iodine. In the absence of radiation exposure, the incidence of thyroid cancer increases with age.
The features of the course of thyroid cancer are the erasure of the clinical picture, the painlessness of palpable nodes, early metastasis to lymph nodes and other organs (in some forms of cancer). Benign nodular formations of the thyroid gland are much more common than malignant ones (90%-95% and 5%-10%, respectively), which requires a thorough differential diagnosis.
Causes
Studies confirm that thyroid cancer develops in 80% of cases against the background of an existing goiter, and its frequency is 10 times higher in goiter-endemic areas. Also, a number of high-risk factors contribute to the development of oncology:
- the presence of chronic inflammatory processes in the thyroid gland;
- prolonged inflammatory or tumor processes of the genital area and mammary glands;
- hereditary predisposition to dysfunction and tumors of the endocrine glands;
- general or local (head and neck areas) X-ray or ionizing radiation, especially in childhood and adolescence;
- thyroid adenoma, regarded as a precancerous disease;
- a number of hereditary genetic conditions (familial polyposis, Gardner syndrome, Cowden’s disease, familial forms of medullary thyroid carcinoma, etc.);
- conditions associated with changes in hormonal balance in the female body (menopause, pregnancy, lactation). More often, a mutual combination of a number of factors plays a role in the development of thyroid cancer.
Classification
According to the international classification of thyroid tumors, there are: epithelial tumors of a benign and malignant nature, as well as non-epithelial tumors. According to histological forms, the following types of thyroid cancer are distinguished: papillary (about 60-70%), follicular (15-20%), medullary (5%), anaplastic (2-3%), mixed (5-10%), lymphoma (2-3%).
The classification of thyroid cancer according to the international TNM system is based on the criterion of the prevalence of tumors in the gland and the presence of metastases in lymph nodes and distant organs, where:
T – prevalence of thyroid cancer:
- T0 — during surgery, the presence of a primary tumor in the thyroid gland was not detected
- T1 is a tumor with the largest diameter up to 2 cm, not spreading beyond the borders of the thyroid gland (i.e. not sprouting into its capsule)
- T2 is a tumor >2 cm, but
- T3 is a tumor > 4 cm in the largest diameter, not spreading beyond the borders of the thyroid gland or a tumor of a smaller diameter, with germination into its capsule
T4 — this stage of thyroid cancer is divided into 2 sub – stages:
- T4a is a tumor of any size with the germination of the capsule of the thyroid gland, subcutaneous soft tissues, larynx, trachea, esophagus or recurrent laryngeal nerve
- T4b is a tumor with the germination of the prevertebral fascia, carotid artery or retrosternal vessels;
N – presence or absence of regional metastases:
- NX — tumor metastasis to cervical lymph nodes cannot be assessed
- N0 — no regional metastases
- N1 — regional metastases are detected (in paratracheal, pretracheal, prelaryngeal, lateral cervical, retrosternal lymph nodes);
M – the presence or absence of metastases to distant organs:
- MX — distant tumor metastasis cannot be assessed
- M0 — there are no distant metastases
- M1 — distant metastases are detected
Classification of thyroid cancer according to the TNM system is used to stage the tumor and predict its treatment. There are four stages in the development of neoplasia (from the most to the least favorable):
- I – the tumor is located locally, the thyroid capsule is not deformed, there are no metastases
- IIa is a single tumor deforming a gland or multiple nodes without metastases and capsule deformation
- IIb – the presence of a tumor with unilateral metastatic lymph nodes
- III – a tumor that sprouts a capsule or squeezes neighboring organs and tissues, as well as the presence of bilateral lymph node lesions
- IV is a tumor with germination into surrounding tissues or organs, as well as a tumor with metastases to nearby and (or) distant organs.
Thyroid cancer can be primary (if the tumor initially occurs in the gland itself) or secondary (if the tumor grows into the gland from neighboring organs).
Types
Papillary thyroid cancer accounts for up to 70% or more of all cases of malignant neoplasms of the thyroid gland. Microscopically, papillary carcinomas have multiple papillary protrusions, which determined their name. The tumor develops extremely slowly, more often occurs in one of the lobes of the glands, and only 10-20% of patients have a bilateral lesion. Despite the slow growth, papillary thyroid carcinoma often metastasizes to the cervical lymph nodes. The prognosis for papillary thyroid cancer is relatively favorable: most patients have a high percentage of 25-year survival. Significantly aggravates the prognosis of cancer metastasis to lymph nodes and distant organs, the age of patients older than 50 and younger than 25 years, tumor size > 4 cm.
Follicular thyroid cancer is the second most common type of malignant thyroid tumor, occurring in 5-10% of cases. It develops from follicular cells that make up the normal structure of the thyroid gland. Pathogenetically, the occurrence of follicular thyroid cancer is associated with a lack of iodine in food. In most cases, this type of cancer does not spread beyond the gland, metastases to lymph nodes, bones and lungs are less common. The prognosis is less favorable compared to the papillary morphological form of cancer.
Anaplastic thyroid cancer is a rare form of malignant tumor that tends to rapid growth, damage to neck structures and spread in the body with an extremely unfavorable prognosis for life. It usually develops in elderly patients against the background of a long-term observed nodular goiter. Rapid growth of the tumor with impaired functions of mediastinal structures (suffocation, difficulty swallowing, dysphonia) and germination of nearby organs leads to the development of a fatal outcome within a year.
Medullary thyroid cancer (carcinoma) is a form of malignant tumor that develops from parafollicular (C–cells) of the gland and accounts for about 5% of cases. Even before the primary tumor is detected in the thyroid gland, it can metastasize to the lymph nodes, liver and lungs. Cancer-embryonic antigen and elevated calcitonin synthesized by the tumor are detected in the patient’s blood. The course of medullary thyroid cancer is more aggressive compared to follicular and papillary cancer, with early development of metastases in nearby lymph nodes and spread to muscles, trachea, lungs and other organs.
Thyroid lymphoma is a tumor that develops from lymphocytes against the background of autoimmune thyroiditis or independently. There is a rapid increase in the size of the thyroid gland with the involvement of lymph nodes and symptoms of compression of the mediastinum. Lymphoma responds well to treatment with ionizing radiation.
Metastases of malignant tumors of other localizations to the thyroid gland are rare. Metatstatic thyroid lesion is observed in melanoma, cancer of the stomach, breast, lungs, intestines, pancreas, lymphomas.
Symptoms
Usually, patients’ complaints are associated with the appearance of nodular formations in the thyroid area or an increase in cervical lymph nodes. As the tumor grows, symptoms of compression of the neck structures develop: hoarseness of voice, swallowing disorders, shortness of breath, cough, suffocation, pain. Patients have sweating, weakness, decreased appetite, weight loss.
In children, the course of thyroid cancer is relatively slow and favorable. In young patients, there is a predisposition to lymphogenic metastasis of the tumor, in older individuals – to the germination of the surrounding neck organs. In elderly patients, the general signs are more pronounced, there is a rapid progression of pathology, the predominance of high-grade forms of thyroid cancer.
Diagnostics
When the thyroid gland is palpated, single or multiple, smaller or larger nodes of dense consistency are found, soldered to surrounding tissues; limited mobility of the gland, tuberosity of the surface; enlargement of lymph nodes. Instrumental diagnostics includes:
- Ultrasound of the thyroid gland. The size and number of nodes in the thyroid gland are revealed. However, according to ultrasound, benign formations and thyroid cancer are difficult to distinguish, which requires the use of additional imaging methods of the gland.
- Tomography. With the help of magnetic resonance imaging, it is possible to differentiate thyroid cancer from benign nodular formation. Computed tomography of the thyroid gland makes it possible to clarify the stage of the disease. The main method of cancer verification is a fine needle thyroid biopsy followed by histological examination of the biopsy.
- Radionuclide research. Scintigraphy of the thyroid gland is not informative in terms of differential diagnosis of the benign or malignant nature of the tumor, however, it allows you to clarify the degree of prevalence (stage) of the tumor process. During the study, intravenously injected radioactive iodine accumulates in the nodes of the thyroid gland and surrounding tissues. Nodes that absorb a large amount of radioactive iodine are determined by the scans as “hot”, less – “cold”.
Patients with thyroid cancer are characterized by anemia, acceleration of ESR, changes in thyroid function (increase or decrease). With the medullary form of cancer, the level of the hormone calcitonin in the blood increases. An increase in the level of thyroid protein thyroglobulin may indicate a recurrence of a malignant tumor.
Treatment
When choosing a method of treatment for thyroid cancer, the type of tumor, stage and general condition of the patient are taken into account. Today, endocrinology has in its arsenal several effective ways to fight thyroid cancer. Treatment may include surgery, therapy with radioactive iodine or hormones, chemotherapy, radiation. Using a combination of two or more methods allows you to achieve a high percentage of cure for thyroid cancer.
- Surgical treatment. The most radical is the surgical removal of the thyroid gland – subtotal and total thyroidectomy. In thyroid cancer of the I-II degree with the localization of the tumor within one lobe, it is limited to its removal along with the isthmus and suspicious areas of the other lobe. An extended thyroidectomy, including removal of neck muscles, excision of the jugular vein, regional lymph nodes and fatty subcutaneous tissue is indicated for stage III-IV thyroid cancer.
- Radioiodotherapy. In addition to the operation, a course of treatment with radioactive iodine I-131 (from 50 to 150 mCi) is prescribed, destroying thyroid cancer metastases and remnants of thyroid tissue after surgery. Radioactive iodine therapy is most effective in thyroid cancer metastases to the lungs and can lead to their complete disappearance.
- Antitumor therapy. The occurrence of tumor relapses is controlled by examining the level of thyroglobulin in the blood. With progressive metastasis of thyroid cancer, external radiation is used. Radiation and chemotherapy are used for palliative treatment of a common tumor process.
After surgery for thyroid cancer, it is necessary to conduct periodic re-examination to exclude relapses and metastases of the tumor, including lung radiography, ultrasound of the thyroid gland, scintigraphy, examination of the level of thyroglobulin in the blood, etc. After partial or total thyroidectomy, it is necessary to take thyroid hormones (thyroxine) to maintain the concentration of TSH within the lower limit of the norm and reduce the likelihood of recurrence of thyroid cancer.
Forecast
The prognosis is determined by the stage of thyroid cancer at which treatment was initiated, as well as the histological structure of the tumor. The probability of thyroid cancer cure with early diagnosis and moderate malignancy of the tumor reaches 85-90%.
An unsatisfactory prognosis is observed in lymphoma and anaplastic form of thyroid cancer: lethality within six months from the onset of the disease is close to an absolute value. A high degree of malignancy is characterized by the course of medullary cancer, which metastasizes early to distant organs.
Follicular thyroid cancer is less aggressive in prognostic value, papillary and mixed forms have the most benign course. The course of thyroid cancer is more favorable in people of mature age, less so in people older than 60 and younger than 20 years.
Prevention
Extensive prevention of thyroid cancer involves the elimination of iodine deficiency through the use of iodized salt and seafood, X-ray irradiation of the head and neck strictly according to indications. An important part of prevention is timely treatment of thyroid pathology, dynamic monitoring by an endocrinologist of patients at risk: those with thyroid pathology, living in an area with iodine deficiency, exposed to radiation, having family cases of medullary thyroid cancer.
