Thyroid nodules are growths of abnormal tissue that develop on the thyroid gland. These lumps may be solid or cystic and fluid-filled. A solid thyroid nodule is more likely than a cystic nodule to be malignant. More than 90% of all solid nodules, however, are benign.
The thyroid is a butterfly-shaped endocrine gland that regulates a variety of hormone interactions, including the pace at which the body burns energy, manufactures proteins, and maintains heart function. It is comprised of a right lobe and a left lobe, and is located at the base of the throat — below the thyroid cartilage — also known as the Adam's apple. When a cystic or solid thyroid nodule occurs, it is often located at the edge of the thyroid. In this case, the nodule may be experienced by the patient as a lump in the throat. Depending on the size of the patient and the lump, the nodule may be visible in the front of the neck.
One cause of a solid thyroid nodule is thyroid cancer, which is diagnosed in less than 10% of all patients presenting with this type of lump. Another cause is iodine deficiency. Iodine is an essential trace element important to proper physical and mental functions. When too little iodine is consumed, thyroid problems, including nodules, may occur. Hashimoto's disease, a condition characterized by chronic inflammation of the thyroid, may also result in a nodule.
In addition to thyroid cancer, there are several additional types of benign solid thyroid nodules. An inflammatory nodule, caused by chronic inflammation of the thyroid, is one common type of nodule. Colloid nodules are another kind of nodule that may be seen in patients presenting with this type of thyroid mass. These overgrowths of tissue may become large, but do not grow past the area of the thyroid. Still another type of solid thyroid nodule, the hyper-functioning thyroid nodule, produces hormones and may contribute to the onset of hyperthyroidism.
A thyroid nodule may be diagnosed after the patient or physician notices a lump in the front of the patient's neck. Sometimes, however, the nodule is incidentally detected during an imaging test for another reason. Once the nodule is discovered, a doctor will often order a blood test to check the thyroid hormone level.
Regardless of the results, the physician will also usually order a thyroid ultrasound to determine if the nodule is a solid thyroid nodule or is cystic. A fine needle biopsy of the thyroid, an in-office procedure to remove cells from the nodule, is also typically performed. A pathologist analyzes the collected cells, and if they are suspicious for cancer, the biopsy may be repeated or the nodule may be surgically removed to make a final diagnosis. A thyroid scan, a test that uses radioactive iodine to help determine if the nodule is malignant or benign, may also be used in the diagnostic process.