This page was last updated: November 14, 2010
Thyroid Nodules
What is a thyroid nodule?
The term thyroid nodule refers to any abnormal growth of thyroid tissue that forms a lump within the thyroid gland. A nodule that is filled with fluid (colloid) is called a thyroid cyst. Roughly, 1/3 of thyroid nodules are cystic and 2/3 are solid. In the United states, thyroid nodules are among the most common endocrine problems. They can be found in up to 50% of the population.The chances are 1 out of 10 that you or someone you know might develop a thyroid nodule. Because of the possibility that a nodule contains cancer is 5-8%, it is imperative that these nodules be taken seriously.
What are the symptoms of a thyroid nodule?
Most thyroid nodules do not cause symptoms and are initially discovered during a routine physical examination. Occasionally, the patient may notice a lump in the neck and seek medical advice.
If they cause symptoms, these fall into three categories:
1) Symptoms of elevated thyroid hormone (hyperthyroidism) in nodules that produce an excessive amount of thyroid hormone. The most common symptom would be heart palpitations caused by a rapid heart rate (rapid pulse). occasionally, a tremor is noticed in the fingers. Bulging eyes may also be an early sign of hyperthyroidism.
2) Symptoms of decreased thyroid hormone (hypothyroidism), caused by a painful inflammation of the thyroid (Hashimoto's thyroiditis) or by iodine deficiency.
3) symptoms caused by compression of adjacent organs. These may include neck pain, radiating to the jaw or ear. Difficulty in swallowing from compression of the pharynx and esophagus. Difficulty in breathing from windpipe (tracheal) compression. Hoarseness is rare. It may indicate irritation of the nerve to the vocal cord, however, this may be an ominous sign of thyroid cancer.
How are the thyroid nodules diagnosed?
Physical Examination:The vast majority of thyroid nodules are diagnosed during a routine physical examination of the neck or accidentlly discovered by the patient looking in a mirror. Occasionally, they are discovered on an ultrasound examination of the neck during a health fair or on an MRI scan of the cervical spine.
Thyroid Function Tests: Blood tests for thyroid hormone (Thyroxine), T4 or thyroid-stimulating hosmone (TSH) are obtained to determine if the thyroid is functionning correctly. They do not indicate whether there is a thyroid nodule or not. In fact, most patients with thyroid nodules have normal thyroid function tests.
Thyroid Ultrasound: An ultrasound examination of the neck is probably the most helpful study. It measures the size of the thyroid lobes and determines whether there is a single nodule or multiple nodules.
Thyroid Scan: A radioactive iodine thyroid scan determines whether the thyroid nodule is functioning and producing thyroid hormone. A functioning nodule contains cells that take up radioactive iodine and, therefore, the nodule would emit a strong signal on the nuclear scan. This is called a "hot" nodule. On the other hand, if the nodule is not functionning normally and is not producing thyroid hormone, it would not emit a signal on the scan. This is called a "cold" nodule. Because cancerous cells do not take up iodine as well as non cancerous cells, cancerous nodules are are more likely to take the form of a cold nodule on a nuclear thyroid scan.
FNA (Fine Needle Aspiration) aka Fine Needle Aspiration Biopsy: In this office procedure, a fine needle is introduced under local anesthesia into the thyroid nodule. Several samples are taken from various locations in the nodule. The specimen which consists of thyroid cells is examined by the pathologist in a manner similar to a Pap Smear.
- In 50% to 60% the cells are non cancerous (benign). The risk of overlooking a cancer is about 3%
- In 5% the result is papillary cancer and the treatment is surgical
- In 10% the result shows follicular cells which could be a follicular adenoma or could be a follicular cancer. In this category, the risk of cancer is 20-30%. A majority of studies have shown that up to 20% of the thyroid lesions classified as follicular neoplasm /suspicious for follicular neoplasm are found to be malignant on surgical excision. This percentage may be higher in Hurthle cell lesions if the nodule is equal to or larger than 3.5 cm in greatest dimension.
- Up to 20-25% of FNAs are reported as being indeterminate or non-diagnostic, meaning that not enough cells were aspirated to be able to make a diagnosis. When these nodules are removed,15-20% are cancerous and the rest are noncancerous follicular or hurtle cell adenomas.
