Thyroid nodules are collections of abnormal cells that form lumps in the thyroid gland. Between 90 and 95 percent of these nodules are noncancerous (benign). However, in uncommon cases, nodules are cancerous (malignant). For this reason, patients are urged to have nodules checked by a physician.

Thyroid nodules are the most common endocrine condition in the United States, according to the American Thyroid Association. Patients may have one nodule or several. In most cases, experts do not know why they form. However, several risk factors are associated with the development of noncancerous and cancerous thyroid nodules, including age.

In many cases, patients with thyroid nodules do not experience any symptoms and are unaware of their condition. However, some patients may discover a lump in the front portion of their neck that appears to grow larger over time. Large nodules that press against the esophagus (tube that carries food from the throat to the stomach) or trachea (windpipe) may cause breathing or swallowing difficulties.

Thyroid nodules are often discovered by a physician during a routine physical examination. In other cases, they may be discovered when a patient is undergoing an imaging test related to another condition.

A fine-needle aspiration biopsy is the primary diagnostic test used to determine whether or not a nodule is cancerous. In a large majority of cases, the biopsy provides enough information to formulate an accurate treatment plan. Blood tests may also be performed.