Thyroid nodules, a very common disease, have been shown to occur in about 4% of adults, and are especially common in middle-aged women. Thyroid nodules are divided into two categories: benign and malignant, with benign nodules accounting for the majority and malignant nodules for less than 1%. A variety of clinical thyroid disorders, such as thyroid degeneration, inflammation, autoimmunity, and neoplasia, can manifest as nodules. Thyroid nodules can be solitary or multiple, and multiple nodules have a higher incidence than solitary nodules, but solitary nodules have a higher incidence of thyroid cancer.
1.Overview
Experts point out that thyroid nodules are a very common disease, especially among middle-aged women. The incidence of this disease is increasing year by year, therefore, we need to detect and treat this disease early. Thyroid nodules can be clinically classified into many categories, each with different symptoms. For example: nodular goiter is common in middle-aged women; inflammatory nodules infective inflammatory nodules, subacute thyroiditis caused by viral infection, subthyroiditis is clinically associated with fever and localized pain in the thyroid gland in addition to thyroid nodules.
2.Pathophysiology
A round or oval shaped mass with an intact envelope, smooth surface and tough texture, ranging in size from a few millimeters to several centimeters, is visible to the naked eye. According to the histological pattern, they can be divided into follicular, papillary and mixed types. Their common features are: most of them are single nodules with intact envelope thyroid nodules; the tumor tissue structure is obviously different from the surrounding thyroid tissue; the internal structure of the tumor has relative consistency; and the surrounding tissues are under pressure. For example, follicular adenomas can be further classified into embryonal, fetal, glial, and Hürthle cell types (eosinophilic tumors) according to the size of the follicles and the amount of glial material they contain. Papillary adenomas are less common (now called papillary follicular adenomas) and are mostly cystic in nature, hence the name papillary cystadenoma. The papillae consist of a single layer of cuboidal or low columnar cells surrounding blood vessels and bundles of connective tissue. Thyroid adenomas with papillary structures have a greater propensity for malignancy and should be diagnosed with caution. Any infiltration of the envelope or vascular invasion should be classified as papillary adenocarcinoma. If there are 1-2 grade papillary branches, neatly arranged tumor cells, small anomalous nuclei, occasional schizophrenia, and intact envelope, it can be temporarily treated as papillary adenoma, but regular postoperative follow-up is needed for recurrence or metastasis.
3. Clinical manifestations
(1) Nodular goiter
It is common in middle-aged women. In the absence of thyroid hormone in the body, the pituitary gland secretes more TSH. Under the long-term stimulation of this increased TSH, the thyroid gland undergoes repeated or continuous hyperplasia, resulting in uneven enlargement and nodule-like changes. There may be bleeding, cystic changes and calcifications within the nodules. The size of the nodules can range from a few millimeters to several centimeters. The main clinical manifestation is an enlarged thyroid gland with multiple nodules of varying sizes on palpation. Patients have few clinical symptoms, usually only anterior neck discomfort, and thyroid function tests are mostly normal.
(2) Inflammatory nodules
Infectious and non-infectious nodules are divided into two categories, the former is mainly caused by viral infection of subacute thyroiditis, other infections are rare. The latter is mainly caused by autoimmune thyroiditis, mostly seen in middle-aged and young women, the patient’s conscious symptoms are less, the examination can find multiple or single nodules, hard and tough texture, less pressure pain, thyroid function tests show thyroglobulin antibodies and The thyroid function tests often show strong positivity for thyroglobulin and thyroid microsomal antibodies.
(3) Nodular toxic goiter
The disease starts slowly and often occurs in patients who have had nodular goiter for many years, mostly at the age of 40 to 50 years or older. When the thyroid gland is palpated, a smooth round or oval nodule with clear borders and a hard texture can be found, which moves up and down with swallowing. Thyroid function tests show elevated thyroid hormone in the blood. If the nodule is functionally autonomous, a nuclear scan shows a “hot nodule”.
(4) Thyroid tumors
These include benign thyroid tumors, thyroid cancer and metastatic cancer.
(5) Thyroid cysts
Most of them are formed by degenerative changes of goiter nodules or adenomas, containing blood or slightly mixed liquid, with clear borders and hard texture. In a few patients, the cyst is caused by a congenital thyroglossal cyst or a remnant of the fourth gill slit.
4.Examination
(1) Nuclear scan
The scan is less significant in distinguishing benign from malignant lesions. Most benign and malignant substantial nodules are hypofunctional relative to the surrounding normal glandular tissue; therefore, detection of cold nodules is rarely specific, and overlapping uptake of nuclide from surrounding normal glandular tissue can miss small nodules. Many thyroid cancers can uptake Tc, therefore, there are still some cases of cancer in hot nodules.
(2) Serological examination
Abnormal thyroid function does not exclude thyroid cancer but indicates that it is less likely. The presence of hyperthyroidism or decreased TSH are suggestive of autonomous functional thyroid adenoma, nodule or toxic multinodular goiter. Patients with medullary thyroid carcinoma have elevated serum calcitonin levels, but require stimulation with pentagastrin and calcium in the early stages of C-cell proliferation.
(3) Ultrasound diagnosis
Ultrasound is reliable for the diagnosis of cystic lesions. It has little value in distinguishing benign from malignant. However, it is useful in identifying the size of nodules, identifying the site of nodules, and guiding localized puncture.
(4) Fine needle aspiration cytology (FNAC) of the thyroid gland
FNAC results of thyroid nodules have a 90% compliance rate with surgical pathology. There is only a 5% false-negative rate and a 5% false-positive rate. Of course the compliance rate depends on the success rate of the operator and varies widely.
(5) Fine needle aspiration cytology
Useful for nodule management, the widespread use of this method has greatly reduced unnecessary thyroid surgery, improved the detection of intraoperative malignancy, and reduced the cost of thyroid nodule management. The accuracy of fine-needle aspiration cytology examination reaches 70% to 90%, which is related to the experience of aspiration and cytology diagnosis.
(6) Other nuclear tests
Positron emission tomography (PET) can be used to examine nodular thyroid lesions and identify benign and malignant tumors, and proton magnetic resonance seems to identify normal glandular tissue and cancerous tissue.
5.Diagnostic differentiation
The diagnosis of benign or malignant nodules can be made mainly from clinical history, thyroid palpation, nuclear medicine imaging, blood sampling and fine needle cytocentesis. For example, in the elderly, a fast growing thyroid tumor or a single hard or fixed nodule is likely to be a sign of malignancy.
This is a benign subacute thyroiditis, which can be treated with medication and most of them will heal on their own. Malignant nodules are usually hard and unsmooth, and may become adherent to the neck tissue, sometimes in combination with enlarged lymph glands in the neck.
If a functional nodule is shown, the chances of the nodule being cancerous are extremely low – about a 2% chance; if a non-functional nodule is shown, it may be malignant, especially if a single cold (non-functional) nodule has a 20% chance of being thyroid cancer; cancer is often a cold nodule, but most cold nodules are still benign. Therefore, in order to accurately diagnose the benign and malignant nodules before surgery, nuclear medicine scan has been replaced by fine needle cytocentesis.
6. Complications
(1) Nodular goiter
This type of nodule is usually common in middle-aged women. In cases where the body is relatively deficient in thyroid hormones and the pituitary gland is overproducing TSH, repeated or sustained hyperplasia can lead to an uneven increase in the thyroid gland and nodule-like changes.
(2) Nodular toxic goiter
This disease occurs slowly, usually in patients who have had goiters for many years, usually over 40-50 years of age, and is common in women, with symptoms of hyperthyroidism, but without significant symptoms or infiltrative proptosis. The nodules have clear borders, are hard, can move up and down with swallowing, and have no vascular murmur in the thyroid area. This is also a symptom of thyroid nodular disease.
(3) Inflammatory nodules
The former is due to subacute thyroiditis caused by viral infection, while other infections are rare. In addition to thyroid nodules, they are accompanied by fever and localized pain in the thyroid gland. The size of the nodules depends on the extent of the lesion, and the texture of the nodules is tougher; the latter is caused by autoimmune thyroiditis, which is mostly seen in middle-aged and young women.
7.Disease treatment
Common treatments for thyroid nodules.
(1) Cysts can be formed by either benign or malignant degenerative changes. Pure thyroid cysts are rare, and any persistent or recurrent mixed masses should be removed.
(2) A single nodule in the thyroid gland with a hot nodule on a nuclear scan is less likely to be cancerous and can be treated with thyroxine (LT4) suppression therapy or nuclear therapy. Cold nodules mostly require surgical treatment. Any single nodule with rapid development and hard texture, or with enlarged lymph nodes in the neck or in children should be operated early because of the high possibility of malignancy.
(3) Multi-nodular goiter (MNG) is traditionally thought to have less chance of developing cancer in MNG than in a solitary nodule. In contrast, high-resolution ultrasonography has revealed that many people diagnosed with a single nodule are actually multinodular, and it is now believed that there is little difference in the incidence of cancer between the two. Therefore, the first step in the management of MNG is to rule out malignancy. If sTSH is decreased, hyperthyroidism is indicated. If FNA cytology is diagnosed as malignant or suspected malignant, surgery should be performed.
(4) Radiation nodules in the head and neck are prone to thyroid cancer, as early as 5 years after radiation and as late as 30 years after radiation. FNA should be performed to confirm the diagnosis of thyroid nodules after radiation therapy.
(5) Non-palpable nodules In recent years, due to the development of ultrasound, CT and MRI, small non-palpable thyroid nodules can be found accidentally during other examinations. These nodules are usually found in elderly people without a history of thyroid disease, thyroid nodules, or risk factors for thyroid cancer. If the nodules are smaller than 37.5 px, they only need to be followed up and observed.