Doctor's Notes on Thyroid Cancer
Thyroid cancer occurs when the cells of the thyroid gland start to grow abnormally. The thyroid gland is located low in the front of the neck, and is shaped like a butterfly and wraps around the windpipe or trachea. Thyroid cancer originates from one of two different types of thyroid cells: follicular cells or so-called parafollicular, or C cells. There are four major types of thyroid cancers: papillary (includes follicular variant papillary thyroid carcinoma), follicular (includes Hurthle cell and insular carcinoma), medullary, and anaplastic.
Symptoms of thyroid cancer include the presence of a thyroid nodule, or lump, that sometimes can be felt in the front of the throat. In rare cases, other symptoms of thyroid cancer include hoarseness, neck enlargement that causes difficulty breathing or swallowing, cough, neck pain, swollen lymph nodes, heart racing, palpitations, or weight loss.
Thyroid Cancer Symptoms
A thyroid nodule larger than 1 cm that is found to have decreased iodine uptake on a nuclear medicine thyroid scan needs to be evaluated with a fine needle aspiration biopsy.
Thyroid Cancer Causes
There are four major types of thyroid cancers, listed below in order of decreasing frequency:
Papillary (includes follicular variant papillary thyroid carcinoma)
Papillary thyroid cancer (PTC) is the most common type of thyroid cancer and accounts for more than two-thirds of all thyroid cancers. There is a higher risk of developing this tumor in persons who have had previous head and neck radiation.
Most patients will not die from papillary thyroid cancer. They are considered low risk if:
- They are younger than 45 years of age.
- They have small tumors.
- There is no invasion of surrounding structures and no metastasis (distant spread).
The spread of papillary thyroid cancer to lymph nodes may indicate recurrence, but it is not associated with a higher chance of death. If distant metastases occur, the pattern of spread includes the lung, bone, and other soft tissue - usually in older people.
Follicular variant papillary thyroid cancer is a type of papillary thyroid cancer that has a survival rate similar to that of papillary thyroid cancer. Overall, papillary thyroid cancer is associated with a high survival rate.
Follicular (includes Hurthle cell and insular carcinoma)
Follicular thyroid cancer (FTC) occurs more in older patients compared to papillary thyroid cancer. The diagnosis of "malignancy" depends on the spread to local tissue and blood vessels. Like papillary thyroid cancer, the patient's age, size of tumor, and the extent that the tumor has spread can predict severity of disease.
Like papillary cancer, follicular cancer develops from the follicular cells and tends to grow slowly.
Variants of follicular thyroid cancer include insular carcinoma and Hurthle cell carcinoma of the thyroid. These tumors are less likely to concentrate radioactive iodine.
Medullary carcinoma of the thyroid originates from the thyroid parafollicular, or C cells. C cells produce a hormone called calcitonin, which can be measured and used as a marker of medullary carcinoma. Medullary carcinoma can occur "sporadically" with no association, with other endocrine diseases, or may have a genetic basis when associated with familial medullary carcinoma or the multiple endocrine neoplasia syndromes (MEN). Multiple endocrine neoplasia syndromes are a group of endocrine diseases that result from an inherited gene mutation. With multiple endocrine neoplasia syndromes which include medullary carcinoma of the thyroid, the adrenal glands, the parathyroid glands, and the surface of the mouth may be affected in addition to the thyroid.
The manner of presentation is different when comparing the sporadic form usually presents with a solitary thyroid mass, whereas the hereditary form usually presents with bilateral thyroid masses in a multifocal fashion.
Medullary carcinoma can include multiple tumors in both lobes of the thyroid and frequently spreads to local lymph nodes, both in the neck and the mediastinum.
Anaplastic thyroid cancer
Anaplastic thyroid cancer is a rare and fast-growing type of thyroid cancer.
Some genetic mutations are related to some thyroid cancers. Damage to DNA can cause these gene mutations due to changes that occur during the natural aging process, radiation exposure, or radiation treatments (as used in the past for skin conditions and head and neck conditions).
Anaplastic thyroid cancer typically occurs in older patients and accounts for less than 5% of all thyroid cancers. One-fifth of these patients may have a current history of another cancer, including a more common form of thyroid cancer. Anaplastic cancer is the most aggressive thyroid cancer. Local invasion and distant spread occur rapidly to other sites, including lymph nodes and the lungs.
It's hard to tell if you have thyroid abnormalities. You might feel run down and tired, or have what is known as "brain fog." You may be gaining weight, pregnant, or experiencing hair loss. Others may feel "hyper," anxious, or sweat a lot more than usual. All of these are common symptoms of thyroid disorders. The thyroid gland regulates many processes within the body, and women are particularly likely to have disorders that affect the function of this essential gland. Recognizing and treating these conditions is critical for optimum health and preventing long-term health problems.
Thyroid : Test Your Medical IQ QuizQuestion
Where is the thyroid gland located?See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.