The term thyroid nodule refers to an abnormal growth of thyroid cells that forms a lump within the thyroid gland.
The thyroid and parathyroid glands are hormone secreting organs that reside in the neck. The thyroid, which is slightly smaller than a person's fist is located in the front part of the neck just in front of the trachea (windpipe) and has two lobes. This organ serves to help regulate the bodies metabolism by secreting thyroid hormone. The release of this hormone is regulated by secretion of other hormones from the pituitary gland.
Because the thyroid gland itself is hormonally responsive, over secretion of pituitary hormones or secretion of substances that act like these hormones stimulate the thyroid gland and make it enlarge (a goiter). The most common reasons for this include diseases such as Hashimoto's thyroiditis, Grave' Disease and multinodular goiter. If the gland grows sufficiently large it can cause symptoms such as difficulty with breathing upon lying flat or with exertion, cough, voice changes and difficulty swallowing. These patients are in general candidates for removal of the thyroid gland. In addition, although many goiters may be treated via thyroid suppression or radioactive iodine, depending on the patient's symptoms or personal preference, these individuals may benefit from having their thryoid gland removed.
A second reason patients may need to have their thyroid gland removed is because of a solitary nodule. Approximately 10% of the population has such nodules and with more sophisticated imaging techniques these growths are being picked up earlier and with a higher frequency. The vast majority of these nodules are benign, however about 10% of these harbor a cancer. The best way to determine which nodules harbor cancer is by inserting a small needle into the thyroid gland and extracting some cells to be examined under a microscope. This is known as a fine needle aspiration (FNA). Approximately 90% of the time the FNA gives a definitive diagnosis. If the diagnosis is definitive and the nodule is benign it will be observed, and if it harbors cancer the thyroid gland or occasionally the affected lobe will need to be removed. Although this is true, 10% of the time the results of the FNA come back "indeterminate." If this occurs the surgeon and endocrine doctor often will recommend removing the lobe of the thryoid that contains the nodule so a pathologist can examine the whole region under a microscope. If this nodule does turn out to harbor cancer (approximately 10% of the time), then the patient will need to have the second lobe removed at a later date.
The most common type of thyroid cancer is papillary cancer. The vast majority of the time this tumor is confined to the thyroid gland. Occasionally this tumor can spread to the lymph nodes in the center of the neck, to other nodes in the neck or to distant sites in the body. If the tumor has spread to the lymph nodes, the surgeon will remove these nodes in either a central neck dissection (if just in nodes in center of neck) but occasionally the patient will need a formal neck dissection (for more information about neck dissection click here). Often after surgical removal of the gland for papillary cancer you endocrinologist will recommend that the patient undergo radioactive iodine to remove any traces of the cancer left in the neck. For larger tumors this improves the local control rate, as well as the overall survival in patients with thyroid cancer.
Other types of thyroid cancer are called follicular, medullary, hurthe cell and anaplastic. Your endocrinologist and your surgeon will discuss what treatment is necessary for these types of tumors. Most often removal of the whole thyroid gland will be necessary, and often either post-operative radioactive iodine, external beam radiation or chemotherapy will be offered.
When a surgeon operates on the thyroid gland there are several important structures which lie in close proximity and as a result may be placed at risk. The most critical structures which lie in close proximity to the thyroid gland are the nerves which move the vocal cords, the recurrent laryngeal nerves. These nerves lie deep to the thyroid gland and just to the sides of the trachea are identified and preserved but may be stretched or injured during dissection. Although this is almost always temporary, on rare occasion (about 1%) permanent paralysis can occur. The most common time for the nerve to be injured are in glands with large tumors or with large goiters. This may result in abnormal position of the nerve and put it at higher risk. By the same token the parathyroid glands which help regulate body calcium lie near, or are intimately associated with the thyroid gland. These glands four glands are identified and preserved, but occasionally their blood supply is interrupted and a patient may develop low calcium levels. Your doctor will monitor this closely in the immediate post-operative period.