A goiter simply means an enlarged thyroid. A goiter can either be a simple goiter where the whole thyroid is bigger than normal or a multinodular goiter where there are multiple nodules. Multinodular goiters can be either a toxic multinodular goiter (i.e. makes too much thyroid hormone and causes hyperthyroidism. See Hyperthyroidism ».) or non-toxic (i.e. does not make too much thyroid hormone). It is not known what causes multinodular goiters in most cases, but iodine deficiency (i.e. too little iodine in the diet) and certain genetic factors have been shown to lead to multinodular goiters.
Signs and Symptoms
Most multinodular goiters do not cause symptoms and are discovered on routine physical exam or during a test being done for another reason. Patients with a toxic multinodular goiter may have signs and symptoms of hyperthyroidism. See Hyperthyroidism ».
If the goiter is large enough, patients may have compressive symptoms that can include difficulty breathing (especially when lying flat), food or pills getting "stuck" in the throat, choking sensation, or a fullness in the neck. These symptoms most commonly happen if the goiter is growing down into the chest, called a substernal goiter. If the goiter is large enough, it may be visible.
CAT scan of a very large goiter in the left thyroid lobe
If a multinodular goiter is found or suspected, a thorough history and physical exam should be performed. Important history includes how fast the thyroid is growing, risk factors for thyroid cancer (i.e. family history of cancer and history of radiation therapy to the neck or chest), family history of goiter, hoarseness, and symptoms of hyperthyroidism. Important physical exam findings include a goiter that can be felt, growth down into the chest, and enlarged neck veins.
After a complete history and physical exam, a thyroid ultrasound (USG) should be done. There is no radiation associated with an USG. An USG is the best test to look at the thyroid and will allow the doctor to see the size of the thyroid and specific features of the nodule(s) including: size, number of nodules, if there are calcifications (calcium deposits), echotexture (i.e. how bright or dark it looks on USG), borders, shape, and if it is solid or cystic (i.e. fluid-filled).
The best test to determine if a thyroid nodule is benign or cancer is a fine-needle aspiration biopsy (FNAB). In this test, a small needle (like the needles used for drawing blood) is placed into the nodule either by USG or feeling the nodule with the fingers. Cells are removed from the nodule into the needle (i.e. aspirated) and looked at under the microscope by a specially trained doctor called a cytologist. There are a number of different guidelines as to which nodules should be biopsied, but in general, nodules over 1 cm should be biopsied. If a patient has risk factors for thyroid cancer (especially a family history of thyroid cancer or exposure to radiation therapy) or suspicious findings on USG, then nodules over 0.5 cm should be biopsied. The FNAB may give one of 4 results:
Non-diagnostic: This means that not enough cells were removed to make a diagnosis. Even in the best of hands, this happens in 5 to 10% of FNAB. Typically the FNAB will be repeated. If the nodule grows, then a repeat biopsy will usually be performed. In certain cases, a patient may go straight to an operation to make a diagnosis, especially if the risk of cancer is high or if the patient has had two or more non-diagnostic FNAB in the past.
Benign: This means that there is a 97% chance that the nodule is not cancer. In most cases, patients with a benign biopsy are watched with an USG and physical exam 6 months later, and then at regularly scheduled times. A patient with a benign nodule may still have an operation if the nodule is large, causing symptoms, or cosmetically unappealing.
Malignant: This means that there is a 97% chance that the nodule is cancer, usually a papillary thyroid cancer. See Papillary Thyroid Cancer ». Much less commonly, the FNAB can show a medullary or anaplastic thyroid cancer. Sometimes the cytologist reports that the nodule is "suspicious for thyroid cancer" which means that there is an 80 to 90% chance of cancer, again usually papillary thyroid cancer. Most patients with a FNAB of cancer will have a total thyroidectomy (i.e. removal of the entire thyroid) with or without removal of certain lymph nodes. See Thyroid Surgery ».
Indeterminate: This category includes different readings like: follicular lesion, follicular neoplasm, Hurthle cell lesion, Hurthle cell neoplasm, and atypical cells or atypical lesions. This means that the cytologist cannot tell if the nodule is cancer, but the cells do not look normal. There is a 15 to 20% chance of having thyroid cancer with an indeterminate biopsy. Said another way, 1 out of 5 people with an indeterminate biopsy will have cancer. The only way to make a clear diagnosis of cancer or no cancer is to remove half or all of the thyroid and see if the cells in the nodule are invading (i.e. growing) outside of the nodule into the surrounding thyroid or outside of the thyroid. See Thyroid Surgery ».
Ultrasound guided fine needle biopsy demonstrating the needle (white line) sampling the nodule
The appropriate treatment of a multinodular goiter depends on the size, how fast it is growing, the FNAB results, risk of cancer, if there are compressive symptoms, and whether the goiter is big enough to be cosmetically unappealing. In general, if the goiter is growing quickly, growing steadily over time, is concerning for cancer, is causing compressive symptoms, is growing substernally, or is cosmetically unappealing, it should be removed (i.e. thyroidectomy).