NEWSLETTER
Thyroid Nodule - Management Guidelines
Dr Saeed Mahar Consultant Endocrinologist Ziauddin University Hospital Karachi.
INTRODUCTION TO THYROID NODULES
A thyroid nodule is a discrete lesion within the thyroid gland that is palpably and/or ultrasonographically distinct from the surrounding thyroid parenchyma.
Thyroid nodules are a common clinical problem. They are more common in women than in men. The clinical importance of thyroid nodules rests with the need to exclude thyroid cancer that occurs in 5% - 10% depending on age, gender, radiation exposure history, family history, and other factors. Generally, only nodules larger than 1 cm should be evaluated, because they have the potential to be clinically significant cancers.
What are the symptoms of thyroid nodules?
The vast majority of thyroid nodules do not cause symptoms. However, if the cells in the nodules are functioning and producing thyroid hormone on their own, the nodule may produce signs and symptoms of hyperthyroidism. A small number of patients complain of pain at the site of the nodule that can travel to the ear or jaw. If the nodule is very large, it can compress the esophagus or trachea and cause difficultly swallowing or shortness of breath. In rare instances, a patient may complain of hoarseness or difficulty speaking because of compression of the larynx.
What are the types of thyroid nodules?
Thyroid nodules may be single or multiple. A thyroid gland that contains multiple nodules is referred to as a multinodular goiter. If the nodule is filled with fluid or blood, it is called a thyroid cyst. If the nodule produces thyroid hormone in an uncontrolled manner without regard to the body's needs, the nodule is referred to as autonomous. This type of nodule may cause signs and symptoms of hyperthyroidism. Occasionally, patients with a thyroid nodule may have too little thyroid hormone or hypothyroidism. This is most often seen when the hypothyroidism is due to Hashimoto's thyroiditis, an inflammatory, autoimmune disease of the thyroid gland.
The most common types of noncancerous, single thyroid nodules are colloid. Only a minority of nodules are cancerous. Cancerous nodules are classified by the types of malignant thyroid cells they contain. These cell types include papillary, follicular, medullary, or poorly differentiated (anaplastic) cells. The prognosis for the patient depends largely on the cell type and how far the cancer has spread by the time it is discovered.
How are thyroid nodules diagnosed?
Thyroid nodules usually are discovered by the doctor on a routine physical examination of the neck. Occasionally, a patient may notice a nodule as a small lump in their neck when looking in the mirror. Once a nodule is discovered, a physician will carefully evaluate the nodule.
HISTORY
The doctor will need to take a detailed history, evaluating both past and present medical problems. If the patient is younger than 20 or older than 70 years of age, there is an increased likelihood that a nodule is cancerous. Similarly, if there is any history of radiation exposure (it was actually a standard treatment to apply radiation to the head and neck in the 1950's to treat acne!), difficulty swallowing, or a change in the voice, the nodule is more likely to be cancerous. Although women tend to have more thyroid nodules than men, the nodules found in men are more likely to be cancerous. Despite its value, the history cannot differentiate benign from malignant nodules.
Physical examination
The physician should determine if there is one nodule or many nodules, and what the rest of the gland feels like. If the nodule is fixed to the surrounding tissue (it is not movable), the probability of cancer is higher. In addition, the physical exam should include a search for any abnormal lymph nodes in the nearby area that may suggest the spread of cancer.
Blood tests
Initially, blood tests should be done to assess the function of the thyroid. These tests include the thyroid hormones, thyroid stimulating hormone (TSH) and the Free thyroxine( FT4) hormone. Elevated thyroid hormones and a low TSH suggest hyperthyroidism. Reduced thyroid hormones and a high TSH suggest hypothyroidism.
Ultrasonography
Detect nodules that are not easily felt Determine the number of nodules and their sizes Determine if a nodule is solid or cystic. Be used to assist in obtaining tissue from the thyroid gland or nodule with a fine needle. Despite its value, an ultrasound cannot determine whether a nodule is benign or cancerous.
Radionuclide scanning
Radionuclide scanning with radioactive chemicals is another imaging technique to evaluate a thyroid nodule. The normal thyroid gland accumulates iodine from the blood and uses it to make thyroid hormones. Thus, when radioactive iodine (I 123) is administered intravenously to an individual, it accumulates in the thyroid and causes the gland to "light up" when imaged by a nuclear camera. The rate of accumulation gives an indication of how the thyroid gland and any nodules are functioning. A "hot spot" appears if a part of the gland or a nodule is producing too much hormone. Non-functioning or hypo-functioning nodules appear as "cold spots" on scanning. A cold nodule has a risk of cancer that is higher than a normally or hyper-functioning nodule. Cancerous nodules are more likely to be cold because cancer cells are abnormal and don't accumulate the iodine as well as normal thyroid tissue.
Fine needle aspiration
A fine needle aspirate (FNA) of a nodule, a type of biopsy, is the most common direct way to determine what types of cells are present in the thyroid gland and in nodules. Fine needle aspiration is possible if the nodule is easily felt. If the nodule is more difficult to feel, fine needle aspiration can be performed under the guidance of ultrasound.
Diagnoses that can be made from fine needle aspiration include:
Benign thyroid tissue (non-cancerous), which can be consistent with Hashimoto's thyroiditis or a colloid nodule or cyst.
Cancerous tissue (malignant), consistent with the diagnosis of papillary, follicular, or medullary cancer. The majority are papillary cancers
Suspicious biopsy, showing a follicular adenoma. Though usually benign, up to 20% of these nodules are found ultimately to be cancerous.
Non-diagnostic, usually because not enough cells are obtained.
What is the treatment for thyroid nodules?
If the nodule is benign on cytology, further immediate diagnostic studies or treatment are not routinely required but it need followup.
Because of the difficulty in distinguishing follicular adenomas from follicular cancers, patients with either of these two types of nodules, other nodules that are highly suspicious for cancerous, and, of course, with definite cancer, should undergo surgery if they are healthy enough to withstand surgery, Most thyroid cancers are curable and rarely cause life-threatening problems. Any nodule not removed needs to be watched closely with an examination and follow-up with the physician every 6-12 months. This follow-up may involve a physical examination, ultrasound examination, or both.
If a nodule is causing hyperthyroidism, it is usually benign. Treatment is aimed at preventing the signs and symptoms of hyperthyroidism such as heart failure, osteoporosis, and rapid heart rate, Treatments include destroying the gland using radioactive iodine, blocking the production of thyroid hormone with medications.