What is a Thyroid Mass?

A mass is a medical term for a lump, so the phrase thyroid mass is used to describe a swelling of the thyroid gland. This could be caused by the thyroid itself being swollen or a lump growing on the thyroid, sometimes referred to as a nodule. The thyroid is situated inside the neck, at the lower end of the windpipe and is shaped roughly like a butterfly, with a narrow central part in front of the windpipe and two larger lobes, one at each side. In most cases, a thyroid mass is found to be benign, or non-cancerous, with only about five percent being malignant, or cancerous. Thyroid masses are more commonly found in women than men, in areas where iodine levels are low and in those who have been exposed to radiation.

Generally, the mass does not cause symptoms unless it presses on the windpipe, causing breathing difficulties, or on the esophagus, where it can interfere with swallowing. Thyroid tests may be carried out to measure levels of thyroid hormone in the blood. Abnormally high levels could indicate a thyroid mass is producing hormones, while low levels might demonstrate that the gland as a whole is failing and has enlarged in a last-ditch attempt to make more. The latter occurs in Hashimoto's disease, an autoimmune condition that destroys thyroid tissue and is treated with synthetic thyroid hormone. A thyroid scan, using ultrasound, can reveal details of a swelling, and scans using other technology may be used to give more information.

A benign mass is most likely to be what is called an adenoma. The most common form of adenoma is an overgrowth of the cells in the lining of the thyroid gland. Adenomas may produce extra thyroid hormone, causing a condition known as hyperthyroidism, where the body's functions speed up resulting in symptoms such as sweating, weight loss and fatigue. Hyperthyroidism can be treated with drugs, radiotherapy, or by surgically removing the nodule.

Another kind of benign thyroid mass is a thyroid cyst, which is just a lump full of fluid. This can be simply drained using a needle. If a cyst keeps recurring, it may have to be removed surgically.

Occasionally, a malignant mass arises in the thyroid, requiring referral to an oncology, or cancer, specialist. The most common thyroid cancer is papillary thyroid carcinoma, which occurs more frequently in women in their late 30s. It grows through the neck, sometimes squashing the windpipe, and may spread to the bones and lungs. Most forms of thyroid cancer grow slowly and in many cases they are curable. Treatments used include surgery, radiotherapy and radioactive iodine, which is taken up by thyroid cells and destroys them.