A thyroid nodule is defined as a small lump of tissue (either solid or cystic - filled with fluid), usually more than one quarter of an inch in diameter that may protrude from the neck's surface or may form in the thyroid gland itself. The nodule can be
either benign (non-cancerous) or malignant (cancerous).
Thyroid nodules are more common among older people than among younger people. In most cases, the cause of thyroid nodules is unknown. The only known cause is radiation treatments to the neck during childhood. The vast majority of thyroid nodules are noncancerous (benign). However, because thyroid cancer usually begins as a nodule in the gland, each nodule must be examined to ensure that it is not cancerous (malignant).
Nodules vary in their composition and in whether they produce thyroid hormone. One or many nodules may gradually develop. When many nodules develop, the condition is called a multinodular goiter. If many nodules have developed and hyperthyroidism occurs, the condition is called toxic multinodular goiter.
Most thyroid nodules do not cause symptoms. Some people might have trouble swallowing, or have a feeling of fullness, pain or pressure in the throat or neck. Some people might notice a lump in their neck when they look in the mirror, but most people don't. Often, the lump is found by a doctor during a routine checkup or other tests.
The most important routine aspects of the diagnostic evaluation of solitary thyroid nodules include a thorough history and physical examination, serum TSH level, and FNAB of the nodule, assuming the patient has access to an experienced cytopathologist. Subsequent management of a solitary thyroid nodule depends largely on FNAB diagnosis. Malignant cytopathology usually is an indication for surgical referral. Exceptions may be made in the case of malignant lymphoma, which typically is not managed surgically, and in cases of anaplastic carcinoma, in which surgical intervention may be futile.
Thyroid nodules associated with benign cytopathology on FNAB can be managed without routine surgical referral in most cases, provided adequate follow-up is possible. Treatment of noncancerous nodules depends on the cause and on the symptoms they produce. Nodules that secrete too much thyroid hormone may produce hyperthyroidism, which requires treatment, usually with radioactive iodine. Noncancerous nodules that do not secrete thyroid hormones usually do not require treatment. If the nodules cause discomfort or are cosmetically displeasing, they can be removed surgically.
Thyroid cancer can almost always be treated and cured: Most people with thyroid cancer are still alive 20 years after the cancer is detected. A few rare types of thyroid cancer, particularly anaplastic thyroid carcinoma and thyroid lymphoma, have a poorer outlook.