1. What is a thyroid nodule?
A thyroid nodule is a scattered lesion caused by abnormal local growth of thyroid cells. A “nodule” that is palpable but not confirmed on ultrasound cannot be diagnosed as a thyroid nodule. Nodules that are not palpable on physical examination but are found incidentally on imaging are called “accidental thyroid nodules”.
2. What is the prevalence of thyroid nodules?
Thyroid nodules are very common. The detection rate by palpation in the general population is 3-7%, while the detection rate by high-resolution ultrasound can be as high as 20-76%.
3.What are the key points in the evaluation of thyroid nodules?
5-15% of thyroid nodules are malignant, i.e. thyroid cancer. The clinical management of benign and malignant thyroid nodules varies significantly in terms of the impact on the quality of life (QOL) and the medical costs involved. Therefore, the key point in the evaluation of thyroid nodules is to differentiate between benign and malignant nodules.
4. What are the clinical manifestations of thyroid nodules?
Most patients with thyroid nodules have no clinical symptoms. When combined with abnormal thyroid function, the corresponding clinical manifestations may appear. Some patients may experience hoarseness, pressure, difficulty in breathing/swallowing, etc. due to the tissue around the nodule ****. In some patients, symptoms such as hoarseness, pressure sensation, difficulty in breathing/swallowing may appear.
5. What medical history and test results are risk factors for thyroid cancer
(1) History of head and neck radiation exposure or radioactive dust exposure during childhood;
(2) History of systemic radiation therapy;
(3) History of differentiated thyroid cancer (DTC), medullary thyroid cancer (MTC) or multiple endocrine adenomatosis type 2 (MEN2), familial polyposis, certain thyroid cancer syndromes (e.g. Cowden syndrome, Carney syndrome, Werner’s syndrome), and thyroid cancer syndrome. (2) Family history of thyroid cancer syndromes (e.g., Cowden syndrome, Carney syndrome, Werner syndrome, Gardner syndrome, etc.);
(4) Male;
(5) Rapid nodule growth;
(6) persistent hoarseness, dysphonia, and exclusion of vocal fold pathology (inflammation, polyps, etc.);
(7) With dysphagia or dyspnea;
(8) Irregular shape of the nodule and fixed adhesion to the surrounding tissue;
(9) Pathological enlargement of lymph nodes in the neck.
6.How to follow up the thyroid nodules?
There is no strong evidence on the optimal frequency of follow-up for thyroid nodules. For most benign thyroid nodules, follow-up can be done every 6 to 12 months. For suspected malignant or malignant nodules that have not been treated, the follow-up interval may be shorter. History taking and physical examination, as well as review of the neck ultrasound, are mandatory at each follow-up visit. Some patients (those with abnormal thyroid function found during the initial evaluation, those treated with surgery, TSH suppression therapy or iodine 131 therapy) will also require follow-up thyroid function.
If nodules are found to be significantly growing during follow-up, special attention should be paid to the presence of symptoms, signs (e.g. hoarseness, difficulty breathing/swallowing, fixed nodules, enlarged lymph nodes in the neck, etc.) and ultrasound signs that suggest nodule malignancy. “Significant growth” is defined as an increase in nodule volume of more than 50%, or at least 2 diameter lines of more than 20% (and more than 2 mm), which is an indication for fine needle aspiration (FNAB); for cystic nodules, the decision to perform FNAB is based on the growth of the solid portion.
7.What is differentiated thyroid cancer (DTC)?
More than 90% of thyroid cancers are DTC, mainly PTC and follicular thyroidcarcinoma (FTC), and a few are Hurthle cell or eosinophilic tumors. Most of the DTCs have slow progression, almost benign course and high 10-year survival rate. However, certain histological subtypes (hypercellular type of PTC, columnar cell type, diffuse sclerosis type, solid subtype and extensive infiltration type of FTC, etc.) are prone to extrathyroidal invasion, vascular invasion and distant metastasis, with high recurrence rate and relatively poor prognosis.
8.What are the treatment methods of thyroid cancer?
The most common type of thyroid cancer is differentiated thyroid cancer, which is treated by thyroid surgery, iodine 131 therapy and thyroxine suppression therapy, among which, surgery is the most important, which directly affects the follow-up treatment and follow-up and is closely related to the prognosis. Most of the differentiated thyroid cancers require a combination of these three methods to achieve the best results. The overall trend of DTC treatment is to individualize and integrate the treatment.
9.Which thyroid cancer needs iodine 131 treatment after surgery
Patients with differentiated thyroid cancer who are treated for the first time
T1(<1cm) is not recommended to be treated with iodine 131.
T1(1-2cm) patients with high risk factors can be treated with iodine 131.
T2(2-4cm) Patients with high-risk factors are recommended to apply Iodine 131 treatment.
T3(>4cm, <45 years old) should be treated with iodine 131.
T3(>4cm, ≥45 years old) should be treated with Iodine 131.
T3 (any size, any age, only extraperitoneal microinfiltration)
Patients with high-risk factors can be treated with iodine 131.
T4 (with extraperitoneal infiltration visible to the naked eye) should be treated with iodine 131.
Nx and N0 (no lymph node metastasis) can usually be treated without iodine 131.
N1 (<45 years) Iodine 131 is recommended for patients with high risk factors.
N1 (>45 years old) Patients with high-risk factors are recommended to be treated with Iodine 131.
M1(with distant metastasis) must apply iodine 131 treatment.
Secondly, early recurrence of differentiated thyroid cancer is recommended to apply iodine 131 treatment.
10. Significance of residual thyroid gland cleared by iodine 131
(1) Reduce the recurrence rate and metastasis possibility of thyroid cancer, and reduce the mortality rate
(2) Improving the iodine uptake function of metastatic thyroid cancer foci: it is conducive to the detection and treatment of metastatic foci
(3) Facilitate follow-up: after removing thyroid tissue, cut off the normal source of thyroglobulin (TG), improve the detection of recurrence and metastases by TG, and facilitate the follow-up of disease development by TG.
(4) Whole-body imaging after iodine 131 treatment can detect tiny thyroid metastases, which is beneficial to the formulation of patient treatment and follow-up plan.
11. Indications for iodine 131 treatment of thyroid cancer lesions
Iodine 131 treatment is suitable for DTC metastases (including local lymph node metastases and distant metastases) that cannot be removed surgically but have the function of iodine uptake. The aim of treatment is to remove the lesion or to partially relieve the disease. The efficacy of clearance treatment is directly related to the extent of iodine 131 uptake by the metastases and the retention time of iodine 131 in the lesions, and is also influenced by the patient’s age, the size and location of the metastases, and the radiosensitivity of the lesions to iodine 131. Younger patients have a better chance of being cured, and small metastases in the soft tissues and lungs are easily cleared; metastases that have formed substantial masses or bone metastases with combined bone destruction often have poorer results with focal clearance treatment, even if the lesions are clearly ingested with iodine 131.
Iodine 131 clearance is not recommended for elderly patients, those with other serious diseases or those who cannot tolerate pre-treatment hypothyroidism. Metastases located in critical areas (e.g. intracranial or paraspinal, intra-airway, paragonadal metastases, etc.) are not suitable for iodine 131 focal debridement if they are inoperable, even if the lesions are significantly treated with iodine 131, and should be treated by other methods.
12.Why should patients with thyroid cancer be hospitalized for iodine 131 treatment?
Reasons for medical safety: Iodine 131 treatment after thyroid cancer surgery involves certain medical risks and requires hospitalization for observation and management and prevention of complications after iodine 131 treatment. For example, some patients may experience neck discomfort, and even some patients may experience neck enlargement, tracheal and laryngeal edema after iodine-131 treatment due to more residual thyroid tissue, resulting in breathing difficulties. Some patients develop a sharp decrease in white blood cells, and some also develop acute gastroenteritis causing clinical discomfort, which requires management and prevention. In addition, some patients with other high-risk diseases require hospitalization for observation to avoid aggravation of other high-risk diseases during iodine 131 treatment and medical safety risks.
The reason for radiation safety: Iodine 131 treatment is to take advantage of the thyroid gland’s ability to concentrate iodine, and the given iodine 131 can release beta rays to exert radiation biological effects locally, causing destruction and atrophy of thyroid follicular epithelial cells and thyroid cancer cells, and reducing secretion, so as to achieve the effect of treating hyperthyroidism or residual thyroid cancer, which is currently the treatment of hyperthyroidism and postoperative residual thyroid cancer treatment. It is one of the important tools for the treatment of hyperthyroidism and postoperative residual thyroid cancer. However, since radioactive iodine 131 not only releases β-rays but also emits γ-rays, the latter of which has a certain penetrating ability and may cause radiation hazards to the patient himself and his family members, medical and nursing staff and other normal people in the surrounding area, it is necessary to take shielding isolation measures for a certain period of time when high-dose iodine 131 treatment is performed.
In addition, there is a large amount of radioactive excretion in the early period (especially within the first 1-3 days) when the patient is treated with iodine 131, and this excretion needs special radioactive sewage treatment system, otherwise it will cause contamination of the surrounding environment. Therefore, patients with hyperthyroidism or thyroid cancer treated with high doses of iodine 131 require short-term hospitalization for radiation safety isolation as well as radiation-carrying excreta disposal to protect the community at large and reduce radiation contamination of the surrounding environment.