Only a small number of thyroid nodules are cancerous. But determining which nodules are cancerous can't be done by evaluating your symptoms alone. Most cancerous thyroid nodules are slow growing and may be small when your doctor discovers them. Aggressive thyroid cancers are rare with nodules that may be large, firm, fixed and rapid growing.

Are thyroid nodules cancer? The vast majority — more than 95% — of thyroid nodules are benign (noncancerous). If concern arises about the possibility of cancer, the doctor may simply recommend monitoring the nodule over time to see if it grows. Ultrasound can help evaluate a thyroid nodule and determine the need for biopsy.