Sometimes FNA tests are done with an ultrasound machine to help guide the needle into nodules that are too small to be felt. Using a needle, fluid and cells are removed from various parts of all nodules that can be felt, and these samples are evaluated. The main diagnostic procedure for suspected thyroid cancer is a fine-needle aspiration biopsy of the thyroid nodule. Although many patients are asymptomatic at first, possible symptoms of thyroid cancer include them. It tends to be quite aggressive and is the least likely to respond to typical methods of treatment. Anaplastic thyroid carcinoma is quite rare, accounting for only 1% to 2% of all thyroid cancers. If found, a thyroidectomy may be performed as a preventive measure. Anyone with a family history of MTC should take a blood test to measure calcitonin levels, which may indicate a strong possibility of a genetic predisposition. There are two types of medullary thyroid cancer: sporadic and familial. In everyone except pregnant women, a radioactive thyroid scan is frequently done in order to identify if the nodules are "cold," meaning they have a greater potential to be cancerous. If a case is classified as suspicious, a surgical biopsy may be needed. Only about 1 in 20 FNA tests reveals cancer.

Between 60% and 80% of FNA tests show that the nodule is benign. If discovered before it metastasizes to other parts of the body, it has a good cure rate. Medullary thyroid carcinoma (MTC) makes up 5% to 10% of all thyroid cancers. Papillary and follicular thyroid cancer are the most common types-, an estimated 80% to 90% of all thyroid cancers fall into this category. The treatment and prognosis for thyroid cancer depends on the type. It is estimated that 800 women and 600 men died of thyroid cancer in 2003. There were 22,000 new cases of thyroid cancer in the United States in 2003, and 16,300 of those were women. Thyroid cancer is fairly uncommon and is considered very survivable, but according to the American Cancer Society, its numbers are on the rise. A fine-needle aspiration or needle biopsy of the nodules to determine whether they may be cancerous; Depending on the results of the evaluation, nodules may be left alone and monitored periodically, assuming they aren't causing serious difficulty, treated with thyroid hormone replacement to help shrink them, or surgically removed if they are causing problems with breathing or if test results indicate a malignancy. An ultrasound of the thyroid to determine whether the nodule is solid or fluid filled. A radioactive thyroid scan, which looks at the reaction of the nodule to small amounts of radioactive material.