A thyroid nodule is one of the most common conditions of the thyroid gland and refers to an isolated lesion within the thyroid gland that can be palpated or that is found to be distinct from surrounding tissue on ultrasound. A palpable nodule that is not confirmed by ultrasound cannot be diagnosed as a thyroid nodule. Thyroid nodules are not a single thyroid disorder, but can manifest in a variety of thyroid disorders, including degenerative thyroid disease, inflammation, autoimmune thyroid disease, injury, and neoplastic lesions, which are collectively referred to as thyroid nodules until their nature is clarified.
Epidemiological studies have shown that 5% of women and 1% of men living in non-iodine deficient areas have palpable thyroid nodules. The detection rate of thyroid nodules in the population can be as high as 19% to 67% if examined with high-resolution ultrasound, and 5% to 10% for thyroid cancer.
Thyroid nodules are classified into two categories: benign and malignant, with benign nodules being the majority.
Etiology and pathology of thyroid nodules
The common diseases that cause thyroid nodules are as follows.
(a) Simple goiter
(ii) Thyroiditis
1. subacute thyroiditis
2. chronic lymphocytic thyroiditis
3. aggressive fibrous thyroiditis
(C) Thyroid adenoma
(D) Thyroid cyst
(V) Thyroid cancer
Diagnosis and evaluation of thyroid nodules
The focus of diagnostic evaluation of thyroid nodules is to distinguish the benignity and malignancy of thyroid nodules.
1. Selection of assessment target
All nodules >1cm in diameter may be clinically significant tumors and therefore need to be evaluated. Nodules ≤1cm in diameter also need to be evaluated if ultrasound indicates suspicion of cancer or if there is a history of head or neck radiation exposure or family history of thyroid cancer.
2.Contents and methods of evaluation
The evaluation of thyroid nodules includes comprehensive history taking and physical examination as well as laboratory, imaging and cytological examinations.
History taking and physical examination should focus on the parts related to thyroid cancer, such as history of head and neck radiation exposure, history of total body irradiation before bone marrow transplantation, family history of thyroid cancer, history of nuclear exposure (before age 14), whether thyroid nodules are growing rapidly, whether there is hoarseness, vocal cord paralysis, and enlarged and fixed ipsilateral cervical lymph nodes.
Laboratory tests include serum thyroid stimulating hormone (TSH), serum thyroglobulin (Tg) and serum calcitonin. A low TSH indicates that the nodule may be secreting thyroid hormones. An increase in TSH suggests the possibility of Hashimoto’s thyroiditis with hypothyroidism. Serum thyroglobulin (Tg) is not specific for the diagnosis of thyroid cancer and is only used to monitor recurrence or metastasis after thyroid cancer surgery or isotope therapy.
Serum calcitonin measurement is not routinely performed. Serum calcitonin >100 pg/ml in unstimulated cases suggests the possible presence of medullary thyroid carcinoma.
Imaging tests include thyroid ultrasound and thyroid nuclide imaging. When the serum TSH level is lower than normal, thyroid nuclear scan should be performed to understand the functional status of the nodule. If the nodule is functional, cytology is not required; if the serum TSH level is normal or above normal, thyroid ultrasonography should be performed to assess the size, location, nature, and proportion of cystic nodules. Solid nodules with microcalcifications, hypoechogenicity and abundant vascularity, irregular margins and ipsilateral cervical lymph node enlargement are likely to be malignant. Echo-free lesions and homogeneous high
Echogenic lesions have a lower risk of carcinogenesis.
Fine needle aspiration biopsy (FNA) of the thyroid gland is the most accurate and effective method for evaluating thyroid nodules, with a 90% concordance rate with surgical findings, but with a 5% false negative rate and a 5% false positive rate. There are four types of results: benign, malignant, suspicious malignant and undiagnosable. Non-diagnostic refers to biopsy results that do not meet specific existing diagnostic criteria, due to operator inexperience, too few aspirates, too small nodes, or the presence of cystic lesions, requiring repeat procedures, preferably under ultrasonographic guidance.
Some cystic or solid nodules that are consistently undiagnosed on the basis of cytologic findings during repeated biopsies are likely to be diagnosed as malignant at the time of surgery.
Evaluation of multinodular goiter: The risk of malignancy in multinodular goiter is the same as the risk of malignancy in a single nodule. Ultrasonography of the thyroid gland is recommended to understand the ultrasonographic features of the nodules. The presence of microcalcifications, hypoechoic solid nodules or abundant blood flow in the nodules suggests the possibility of malignancy, and FNA is performed for this nodule or, in the absence of these features, for the largest of the nodules.
Treatment and management of thyroid nodules
1. Treatment of thyroid nodules
The treatment of thyroid nodules in the Guidelines is based on the results of FNA. If the cytologic results show benign, no further examination and treatment are required; if malignant, surgery; if undiagnosed, repeat biopsy and still undiagnosed, close observation or surgical excision. For suspected malignancy, in addition to functional autonomous nodules, single lobe thyroidectomy or total thyroidectomy is recommended.
2. Follow-up treatment of benign thyroid nodules
Even if a benign thyroid nodule is diagnosed, patients need to be followed up because the false-negative rate of FNA can be up to 5%, which is a small but not negligible percentage of patients. The growth of the nodule itself is not necessarily an indication for malignancy, but it is an indication for a repeat FNA.
Routine use of thyroxine suppression therapy is not recommended. Surgery or radiation therapy may be used for high-functioning adenomas. Benign cystic nodules can be treated with one or more simple fine-needle aspiration, or sclerosing agents (such as tetracycline hydrochloride saline or anhydrous ethanol) can be injected into the cystic cavity after the cystic fluid has been aspirated.
3. Diagnosis and treatment of thyroid nodules in children and pregnant women
The diagnostic evaluation and treatment of thyroid nodules in children are the same as those in adults. In the evaluation of thyroid nodules in pregnant women, thyroid nucleus scanning is not allowed and other evaluation methods are the same as for non-pregnant women. In pregnant women with a diagnosis of a malignant thyroid nodule, ultrasound monitoring should be performed to reduce the risk of miscarriage and surgery should be chosen before 24 weeks of gestation if the nodule continues to grow. If the nodule is stable or if it is diagnosed late in pregnancy, surgery should be performed after delivery. Thyroid cancer detected during pregnancy does not progress faster than in non-pregnant patients, and there is no difference in survival and recurrence rates, and delaying treatment for <1 year has no significant adverse effect on prognosis.
Additional notes on the diagnosis and treatment of thyroid nodules
Regarding the diagnosis and treatment of patients with thyroid nodules and thyroid cancer, there are significant differences between the actual practice in China and the recommended protocols in the above mentioned American Guidelines for the Diagnosis and Treatment of Thyroid Nodules and Differentiated Thyroid Cancer.
Due to the popularization of thyroid ultrasonography, the detection rate of thyroid nodules has reached the international level, but FNA is not well developed and not popular, and there is a lack of unified quality control standards and standardized management. diagnosis.
Because thyroid nodules are very common, hospitals at all levels are performing related surgeries and treatments, and because of the lack of standardized management and guidance, the surgical procedures are varied and postoperative management is not standardized. This may affect the outcome of treatment.
In view of the actual situation in China, we believe that it is currently difficult to completely copy the US Guidelines for the Diagnosis and Treatment of Thyroid Nodules and Differentiated Thyroid Cancer in our country, and it is not in line with our specific national situation. However, it is necessary for us to study and understand the content of the Guidelines for the diagnosis and treatment of thyroid nodules and differentiated thyroid cancer, and to develop our own guidelines tailored to our specific situation, so that both patients can receive proper treatment and unnecessary surgery can be reduced.
About 80-90% of all thyroid nodules are nodular goiter, which is not a tumor and is a benign lesion and does not require surgery according to the U.S. Guidelines for the Management of Thyroid Nodules and Differentiated Thyroid Cancer. However, due to the low level of ultrasound and cytology diagnosis in most hospitals in China, it is impossible to distinguish the benign and malignant nature before surgery, so that some physicians operate on all patients with thyroid nodules, which not only wastes a lot of medical resources, but also causes different degrees of damage to the patients’ appearance and function, etc.
Combined with the current state of medical care in China, different guidelines for diagnosis and treatment can only be adopted according to the actual level of medical care in different regions and hospitals. Some large hospitals such as Beijing and Shanghai, which are in a position to do so, should align with the U.S. Guidelines for the Diagnosis and Treatment of Thyroid Nodules and Differentiated Thyroid Cancer as far as possible, relying mainly on ultrasonography and FNA cytology results to determine whether surgical treatment is needed, and the scope of surgical resection can be guided by the frozen section results during surgery to avoid waste and damage caused by overtreatment.
Large hospitals at the provincial and municipal levels can rely mainly on the ultrasonographic features provided by ultrasonography for surgical selection, such as the presence of microcalcifications in nodules, hypoechoic solid nodules with abundant blood flow in the nodules, suggesting the possibility of malignancy can be operated directly, and intraoperative then judge the benignity and malignancy according to frozen sections.
If the ultrasound diagnosis in the primary unit does not provide useful information, direct surgery may also be considered when the patient’s history and examination show the following.
(1) Previous radiation therapy to the head and neck;
(2) Family history of medullary thyroid carcinoma or multiple endocrine neoplasia type II;
(3) Age <15 years or >45 years;
(4) Male with a single solid nodule;
(5) Hoarseness, dysphagia, dyspnea, etc.
(6) Fast-growing nodules;
(7) hard nodules;
(8) Fixed nodules;
(9) Nodules >4 cm;
(10) Enlarged ipsilateral cervical lymph nodes.
Cystic thyroid lesions are mostly benign and can be treated by simple aspiration. If the aspirated fluid is pure and clear, the nodules can be followed up for 6 months if they disappear completely; if the aspirated fluid is bloody, or if there are residual nodules after aspiration or if they recur soon after aspiration, surgery is indicated. If there are cancer cells or suspected cancer cells in the cystic fluid, surgery should be performed.