Thyroid cancer is a type of cancer that starts in the thyroid gland. Cancer starts when cells begin to grow out of control. (To learn more about how cancers start and spread, see
Thyroid hormones help to regulate your metabolism, heart rate, blood pressure, and body temperature.
Where does thyroid cancer begin?
The thyroid gland is located in the front of the neck, just beneath the thyroid cartilage (Adam’s apple). Most people cannot see or feel their thyroid. It has two lobes — the right and left lobes — that are joined by a narrow piece of the gland called the isthmus (see picture below).
The thyroid gland is made up of two types of cells:
1 Follicular cells use iodine from the blood to produce thyroid hormones, which aid in metabolism regulation. Hyperthyroidism (excess thyroid hormone) can cause a fast or irregular heartbeat, difficulty sleeping, nervousness, hunger, weight loss, and a feeling of being overheated. When a person has too little hormone (hypothyroidism), they slow down, feel tired, and gain weight. The pituitary gland at the base of the brain produces a thyroid-stimulating hormone, which regulates the amount of thyroid hormone released by the thyroid (TSH).
2 C cells (also known as parafollicular cells) produce calcitonin, a hormone that regulates how the body uses calcium
Immune system cells (lymphocytes) and supportive (stromal) cells are also less common in the thyroid gland.
Each type of cell gives rise to a different type of cancer. The distinctions are significant because they influence the severity of cancer and the type of treatment required.
Thyroid gland growths and tumors can take many forms. The majority of these are benign (non-cancerous), but some are malignant (cancerous), which means they can spread to other parts of the body and into nearby tissues.
Thyroid problems that are not serious
Changes in the size and shape of the thyroid gland can frequently be felt or seen by patients or their doctors.
A goiter is a term used to describe an abnormally large thyroid gland. Some goiters are diffuse, which means that the entire gland is large. Other types of goiters are modular, which means the gland is large and contains one or more nodules (bumps). There are numerous reasons why the thyroid gland may be larger than usual, and the majority of the time, it is not cancer. Both diffuse and nodular goiters are typically caused by a hormonal imbalance. For example, a lack of iodine in the diet can result in hormonal imbalances and a goiter
Nodules on the thyroid gland.
Thyroid nodules are lumps or bumps in the thyroid gland. The majority of thyroid nodules are benign, but about 2 or 3 in every 20 are cancerous. These nodules can sometimes produce too much thyroid hormone, resulting in hyperthyroidism. Thyroid nodules that produce excessive amounts of thyroid hormone are almost always benign.
Thyroid nodules can appear at any age, but they are most common in older adults. Thyroid nodules that can be felt by a doctor affect less than one in every ten adults. However, when the thyroid is examined with ultrasound, many more people are discovered to have nodules that are too small to feel, and the majority of them are benign.
The majority of nodules are cysts filled with fluid or colloid, a stored form of thyroid hormone. Solid nodules, which lack fluid and colloid, are more likely to be cancerous. Nonetheless, the majority of solid nodules are not cancerous. Some solid nodules, such as hyperplastic nodules and adenomas, have an abnormally high number of cells, but the cells are not cancerous.
Benign thyroid nodules can sometimes be left alone (not treated) and closely monitored if they are not growing or causing symptoms. Others may require medical attention.
Thyroid Cancer Types
The following are the most common types of thyroid cancer:
1 Papillary, follicular, and Hürthle cell differentiation
3 Anaplastic (aggressive cancer)
Thyroid cancers that have been differentiated
The majority of thyroid cancers are differentiated. When examined in the lab, the cells in these cancers resemble normal thyroid tissue. Thyroid follicular cells are the source of these cancers.
Papillary cancer (also known as papillary carcinomas or papillary adenocarcinomas): Papillary cancer accounts for approximately 8 out of 10 thyroid cancers. These cancers grow slowly and usually affect only one lobe of the thyroid gland. Papillary cancers, despite their slow growth, frequently spread to the lymph nodes in the neck. Even when these cancers have spread to the lymph nodes, they are frequently treatable and rarely fatal.
Papillary cancers are classified into several subtypes. The follicular subtype (also known as the mixed papillary-follicular variant) is the most common. When detected early, it has the same good prognosis (prognosis) as the standard type of papillary cancer and is treated similarly. Other papillary carcinoma subtypes (columnar, tall cell, insular, and diffuse sclerosing) are less common and grow and spread more quickly.
Follicular cancer (also known as follicular carcinoma or follicular adenocarcinoma): Follicular cancer is the second most common type, accounting for approximately one out of every ten thyroid cancers. It is more common in countries where people do not consume enough iodine. These cancers do not usually spread to the lymph nodes, but they can spread to other parts of the body such as the lungs or bones. The outlook (prognosis) for follicular cancer is not as good as for papillary cancer, but it is still very good in the majority of cases.
Hürthle cell carcinoma (also known as oxyphil cell carcinoma): This type of thyroid cancer accounts for about 3% of all cases. It is more difficult to detect and treat.
Thyroid cancer in the medulla
MTC (medullary thyroid cancer) accounts for approximately 4% of thyroid cancers. It develops from the thyroid gland’s C cells, which normally produce calcitonin, a hormone that helps regulate the amount of calcium in the blood. Even before a thyroid nodule is discovered, this cancer can spread to lymph nodes, the lungs, or the liver.
This type of thyroid cancer is more difficult to detect and treat. MTC is classified into two types:
1 Sporadic MTC, which accounts for approximately 8 out of 10 MTC cases, is not inherited (meaning it does not run in families). It primarily affects older adults and frequently affects only one thyroid lobe.
2 Familial MTC is inherited, with 20% to 25% occurring in each generation. These cancers commonly appear in childhood or early adulthood and can spread quickly. Typically, patients have cancer in multiple areas of both lobes. Familial MTC is frequently associated with an increased risk of developing other types of tumors. This is described in more detail in
Thyroid cancer that is anaplastic (undifferentiated).
Anaplastic carcinoma (also known as undifferentiated carcinoma) is a rare type of thyroid cancer that accounts for approximately 2% of all thyroid cancers. It is believed that it can arise from an existing papillary or follicular cancer. The cancer is referred to as undifferentiated because the cancer cells do not resemble normal thyroid cells. This cancer spreads quickly into the neck and other parts of the body and is extremely difficult to treat.
Thyroid Cancers That Are Less Common
Thyroid lymphomas, thyroid sarcomas, and other rare tumors account for less than 4% of thyroid cancers.
Cancer of the parathyroid gland
The parathyroid glands are four tiny glands located behind but attached to the thyroid gland. The parathyroid glands aid in calcium regulation in the body. Cancers of the parathyroid glands are extremely rare, with fewer than 100 cases reported each year in the United States.
Because they cause high blood calcium levels, parathyroid cancers are frequently discovered. This causes fatigue, weakness, and drowsiness. It can also cause you to urinate (pee) a lot, which can lead to dehydration, which can exacerbate your weakness and drowsiness. Other signs and symptoms include bone pain and fractures, kidney stone pain, depression, and constipation.
Larger parathyroid cancers may manifest as a nodule near the thyroid. The only treatment, regardless of how large the nodule is, is surgical removal. Parathyroid cancer is much more difficult to treat than thyroid cancer.