Thyroid cancer can occur in any age group, although it is most common after age 30 and its aggressiveness increases significantly in older patients. The majority of patients present with a nodule on their thyroid which typically does not cause symptoms.
INTRODUCTIONKnow More Thyroid cancer occurs in the cells of the thyroid — a butterfly shaped gland located at the base of your neck, just below your Adam's apple. Your thyroid produces hormones that regulate your heart rate, blood pressure, body temperature and weight. Thyroid cancer might not cause any symptoms at first. But as it grows, it can cause pain and swelling in your neck. Most cases of thyroid cancer can be cured with treatment.
Thyroid cancer can occur in any age group, although it is most common after age 30 and its aggressiveness increases significantly in older patients. The majority of patients present with a nodule on their thyroid which typically does not cause symptoms. Remember, over 99% of thyroid nodules are not cancer! But, when a thyroid cancer does begin to grow within a thyroid gland, it almost always does so within a discrete nodule within the thyroid.
There are four major types of thyroid gland cancer: anaplastic, follicular, medullary and papillary. These types of thyroid cancer look differently under a microscope and generally grow at varying rates.
Anaplastic cancer is the fastest growing type of thyroid cancer. The cancer cells are extremely abnormal and spread rapidly to other parts of the body. Anaplastic cancers make up only about 2 percent of all thyroid cancers and are generally difficult to cure.
This type of cancer also develops in thyroid cells that produce iodine-containing hormones. Most follicular cancers can be cured. About 10 percent to 30 percent of thyroid cancers are follicular cancers. These cancers are well differentiated, meaning slow growing and contain cells that are similar to healthy thyroid cells.
Medullary cancer is more difficult to control than papillary and follicular thyroid cancer. The cells involved in medullary cancers produce calcitonin, a hormone that does not contain iodine. About 5 to 7 percent of all thyroid cancers are medullary cancers.
Of the four types of thyroid cancer, only medullary thyroid cancer can be inherited, which is caused by an alteration in the RET gene. Individuals who inherit this alteration are almost certain to develop medullary thyroid cancer at some time in their lives.
This type of thyroid cancer develops in cells that produce thyroid hormones containing iodine. Papillary cancer is well-differentiated, meaning that it grows very slowly and contains cells that are similar to healthy thyroid cells. Doctors usually can treat these cancers successfully, even when cancer cells have spread to nearby lymph nodes. Papillary cancers account for about 60 percent to 80 percent of all thyroid cancers and have a favorable prognosis.
RISK FACTORS Know More The cause of thyroid cancer remains uncertain as of today. However, scientists have made certain conjectures about its origin and risk factors. These include:
Globally, females are more susceptible compared to males.
Females between 40-50 and males 60-70 have greater chances of contracting the disease.
Exposure to high levels of natural or artificial radiation can cause the disease to occur. It can include instances of radiation therapy to areas of the head and neck, like that of lymphoma.
Genetic disposition to the disease increases the chance of subsequent generations developing it.
It can be due to multiple endocrine neoplasia type 2. Other complexities include Cowden disease and familial adenomatous polyposis.
Prior cases of thyroid diseases, like thyroiditis, can increase the risk.
Iodine is necessary to create thyroid hormones in the body. Iodine deficiency can increase the vulnerability to developing the cancer.
SIGN & SYMPTOMS Know More Most thyroid nodules don't cause signs or symptoms. But occasionally some nodules become so large that they can:
In some cases, thyroid nodules produce additional thyroxine, a hormone secreted by your thyroid gland. The extra thyroxine can cause symptoms of an overproduction of thyroid hormones (hyperthyroidism), such as:
DIAGNOSIS & TREATMENTS Know More Once a thyroid nodule is found, the next step is to determine if the nodule represents a benign (non-cancerous) growth or malignant (cancerous) tumor. A careful physical exam should be done by a healthcare provider, with attention to the examination of the neck to evaluate for the presence of enlarged lymph nodes. You will also have blood tests to check your thyroid function and hormone levels. If these tests show an over-functioning thyroid gland, then additional tests will be performed to determine if the nodule is composed of benign thyroid tissue that is overproducing thyroid hormone.
A biopsy is not usually required for benign, "functioning" nodules. A thyroid scan will help distinguish this nodule. This scan is a nuclear medicine study using radioactive iodine. Functioning thyroid tissue takes up iodine to produce normal thyroid hormones. The small amount of radioactive iodine used to take pictures will be taken up by those areas of the thyroid that are producing thyroid hormone. Thus, a nodule composed of functioning thyroid tissue will appear "hot" in these nuclear medicine scans (i.e., concentrating the radioactive iodine). These "hot nodules" are almost always benign and often require no further workup for thyroid cancer. Nodules that are "cold" (i.e., do not take up much iodine) are also often benign but can be malignant in 15-20% of cases. Therefore, these deserve more attention and further workup.
Most patients (>95%) with thyroid nodules have normal thyroid function and the nuclear medicine thyroid scan is not indicated. For these patients, the next step in investigating a nodule is a thyroid ultrasound.
Ultrasound is an extremely powerful tool in obtaining information about a thyroid nodule. Ultrasound has the ability to provide additional information about a nodule, such as its composition (solid or cystic) and its appearance (hypoechoic or dark versus hyperechoic or bright), which may increase or decrease its likelihood of being cancer. In addition, ultrasound may detect more suspicious nodules that are not able to be detected on a physical exam. Ultrasound may also identify abnormal lymph nodes around the thyroid gland, which could be evaluated at the same time as the thyroid nodule.
If the appearance of the thyroid nodule on ultrasound is suspicious for thyroid cancer, the next step in diagnosis may be a fine-needle aspiration of the nodule (FNA). This procedure is typically viewed as accurate, low risk, and cost-effective to evaluate thyroid nodules for suspected malignancy. Solid nodules that appear dark or hypoechoic on ultrasound that have small calcifications are more likely to be cancerous and FNA is recommended when such nodules are small (1cm), than for fluid filled nodules without these features (>2cm for FNA).
Fine needle aspiration involves placing a thin needle into the nodule, and removing cells from it so that they can be analyzed. Usually, this is done with ultrasound guidance. This means that an ultrasound is performed at the time of the procedure to visualize the needle placement into the nodule. FNA has a diagnostic accuracy of over 98%, though it is highly dependent on the healthcare provider's expertise in performing the test and the pathologist's experience in interpreting the results. Up to 30% of FNA biopsies will return an inconclusive result (including follicular thyroid cancer, which cannot be diagnosed by cytology alone), or an "indeterminate" result. These patients are referred for surgery.
Molecular-based testing is available to help determine which nodules are benign based on their genetic profile. By analyzing the genetic make-up of the sample obtained by FNA, providers can identify patients who most likely have a benign nodule and therefore, can avoid surgery.
If a diagnosis of thyroid cancer is made, additional pre-operative workup will be completed to determine if there is spread of disease to local lymph nodes. In some cases, additional imaging of the neck is required by the surgeon using a CT (usually without IV contrast) or, more commonly, MRI of the neck to evaluate lymph nodes, muscle, or tracheal involvement. In rare cases, evaluation for metastasis to distant areas of the body including the lungs and bones is done prior to surgery.
The treatment of thyroid cancer depends on the type (histopathology) of thyroid cancer that is identified. It can involve multiple types of treatment including surgery, radioactive iodine, radiation therapy, chemotherapy/targeted therapy, and/or thyroid suppressive therapy.
Surgery plays a central role in the treatment of thyroid cancer. The goal of surgery is the removal of the tumor. There are several options for surgical procedures to treat thyroid cancer including :
If the thyroid gland is not completely removed during the first surgical procedure, the patient is always at risk for recurrence in the portion of the thyroid left behind. Additional surgery to remove the remaining portion of the thyroid gland can also be performed.
All patients suspected to have thyroid cancer should have an ultrasound to evaluate the lymph nodes in the neck for spread of the thyroid cancer. If thyroid cancer is found to have spread to these lymph nodes, the surgeon will remove the lymph nodes at the same time the thyroid is removed. However, the role of prophylactic removal of the lymph nodes of the neck when they are not obviously involved is unclear. The lymph nodes very close to the thyroid gland are usually dissected without much difficulty and therefore should be removed.
Depending on the pathologic staging, patients may require additional treatment after surgery. The first and simplest is the use of supplemental thyroid hormone following surgery. Patients with near-total or total thyroidectomies require supplemental thyroid hormone because the thyroid gland is no longer present. In addition, thyroid hormone can also act as a thyroid cancer therapy. The standard of care is to give slightly more thyroid hormone than the patient would otherwise require because this has been shown to keep any remaining thyroid cancer "asleep" or inactive through a feedback system. In other words, if the body detects that there is a sufficient amount of thyroid hormone already present (through supplementation), it will not produce signals to "turn on" the thyroid to grow and produce thyroid hormone itself. This can be quite successful in keeping residual thyroid cancers dormant.
As thyroid tissue, and some thyroid cancers, preferentially take up iodine into their cells as part of normal functioning, the use of radioactive iodine, I-131, (RAI) may also be used to kill any remaining thyroid tissue (called "remnant" ablation) and potentially any thyroid cancer cells. Indications for RAI include tumors with high-risk features, such as sizes >2 cm, invasion of the cancer through the thyroid capsule or into the soft tissues of the neck, spread to the lymph nodes, or more distantly, or recurrent disease (thyroid cancer that has come back). RAI can be a very effective therapy in many cases, though some thyroid cancers do not have the ability to take up iodine, rendering RAI useless.
RAI has been shown to improve the outcome of patients with higher risk disease (specifically for those with Stage II, III, and IV disease). The iodine is taken up into the cell and the radiation within the radioactive iodine itself is released locally, delivering a lethal dose of radiation to these cells. This treatment works well because normal thyroid cells and some thyroid cancer cells preferentially absorb and retain iodine, so other tissues are rarely affected. For the first few days after treatment with RAI, you emit radiation and should avoid close contact with others.
Recent research indicates the use of RAI may increase the risk of the patient developing myelodysplastic syndrome (MDS), especially within the first two years of RAI treatment. Patients and their care teams should weigh the risks of treating low risk, well-differentiated thyroid cancers with RAI.
Radiation therapy can be effective in certain subsets of patients; in particular, those with aggressive types of thyroid cancer, those with a high risk of recurrence, or those with residual disease still present after surgery. High-risk features include incomplete resection, spread outside the thyroid gland to soft tissues of the neck or to regional lymph nodes, certain histological subtypes of thyroid cancer, and those cancers that do not take up RAI. It is also used in many cases of anaplastic thyroid cancer to attempt to halt this aggressive disease.
Chemotherapy has not classically been used in the treatment of thyroid cancer. However, chemotherapy drugs such as paclitaxel, doxorubicin, cisplatin, and carboplatin may sometimes be used in the treatment of metastatic disease, for anaplastic thyroid cancers, or disease that has progressed after RAI or radiation therapy. Doxorubicin, fluorouracil, dacarbazine, used in combination, may be used in the treatment of medullary thyroid cancer. In anaplastic thyroid cancers, dabrafenib, trametinib, entrectinib, and selpercatinib are used.
