Parathyroid cancer, also called parathyroid carcinoma, is a very rare cancer that develops in the parathyroid glands, two pairs of pea-sized glands located next to the thyroid in the front of the neck. The parathyroid glands produce parathyroid hormone (PTH), a chemical that enters the bloodstream and raises calcium levels in the blood. It does this by forcing the bones to release calcium, stimulating the intestines to absorb more calcium from food, and signaling the kidneys to withhold calcium from the urine. Normally, the parathyroid glands have a natural feedback mechanism that allows them to adjust their production of PTH to maintain blood calcium levels in the normal range.

When parathyroid cells become malignant (cancerous), they multiply out of control and typically form a firm, grayish-white tumor that can invade the nearby thyroid gland and neck muscles. As the cancerous cells grow, they usually produce too much PTH. In most cases, the end result is abnormally high levels of PTH in the blood (hyperparathyroidism) with abnormally high levels of calcium in the blood (hypercalcemia). The levels of PTH are so high that they force the bones to pour out critical amounts of calcium, which can cause bone pain and can lead to osteoporosis (thinning of the bones). The elevated PTH also forces the kidneys to retain large amounts of calcium, triggering the formation of kidney stones. Excessively high calcium levels also can cause kidney damage, dehydration and changes in neurological function including confusion. More often, an enlargement of the parathyroid gland may be due to a benign enlargement of the gland, called an adenoma.

Parathyroid cancer is so rare that even a major medical center may see no more than two dozen patients with the illness over a period of several decades. About 1 of every 2,000 people in the United States is diagnosed with hyperparathyroidism in any given year, but only 20 to 40 of these patients have parathyroid cancer. Parathyroid cancer occurs most commonly in adults between 45 and 51 years old, although cases have occurred in people as young as 19 and as old as 81. Because parathyroid cancer is so rare, researchers have not been able to determine whether there are any specific environmental or lifestyle factors that increase the risk of this illness. A few cases have shown an inherited tendency, with several generations of a single family affected.

Symptoms of parathyroid cancer include:

• A small lump in the front of the neck (22% to 50% of cases)
• Kidney stones (pain in the back or side and blood in the urine) and early signs of kidney failure (up to 90% of cases)
• Bone pain and osteoporosis (up to 70% of cases)
• Hoarseness (up to 10% of cases) caused by cancer invading the vocal cords or the nerves to the vocal cords
• Various other symptoms, such as constipation, weak muscles, vomiting or decreased consciousness

Because the rise in calcium can be gradual in patients with parathyroid carcinoma, the body is able to adapt, and patients commonly have only minor symptoms even with calcium levels that would be fatal if they were reached more rapidly.

Most patients with parathyroid cancer visit a doctor because they have kidney symptoms, bone symptoms or both. For this reason, the doctor usually will ask about risk factors related to various types of kidney and bone illnesses. Because parathyroid cancer is so rare, a doctor may never see even one patient with the illness throughout a lifetime of medical practice.

Your doctor probably will begin the diagnostic process with a thorough physical examination and basic laboratory tests, such as a blood tests and urinalysis. Depending on your specific symptoms, your doctor also may order X-rays or special scans of your neck, bones or kidneys. If you have parathyroid cancer, your blood tests most likely will show an abnormally high calcium level. This will lead your doctor to test for hypercalcemia, including a check for high blood levels of PTH, especially if he or she finds a lump on your neck during the physical examination.

The only way to confirm that someone has parathyroid cancer is to remove the tumor surgically and examine it under a microscope.

Parathyroid cancer will continue to grow until it is treated.

Because the risk factors for parathyroid cancer remain unknown, there is no way to prevent it.

Once your doctor confirms that you have parathyroid cancer, your treatment will depend on whether the cancer involves only your parathyroid gland or has spread (metastasized) to other areas. Parathyroid cancer most commonly spreads to the lymph nodes, lungs, bones and liver. If you have cancer that is limited to your parathyroid, then the cancerous parathyroid gland will be removed surgically together with your thyroid gland on the same side. Before surgery, you will receive medication to control your blood calcium levels until your tumor is removed. In some medical centers, radiation treatment is given after surgery.

If your parathyroid cancer has spread to areas outside your parathyroid, then you will need surgery to remove as much of the cancer as possible. This will help to decrease the high levels of PTH and calcium in your blood. Both before and after surgery, you will receive medication to help maintain your blood calcium levels as close to normal as possible. If you cannot be treated surgically, your high calcium levels often can be controlled with plicamycin (Mithracin), pamidronate (Aredia), calcitonin (Calcimar, Cibacalcin, Miacalcin), or, less commonly, gallium nitrates (Ganite). Patients with metastatic parathyroid cancer can choose to participate in clinical trials that are evaluating alternative treatments involving radiation, surgery plus radiation, or chemotherapy.

Call your doctor promptly if you have symptoms of parathyroid cancer, especially if you have bone pain or a lump on your neck.

At the time of diagnosis, most patients with parathyroid cancer have localized disease that can be treated surgically. However, even after a localized tumor is totally removed, parathyroid cancer often comes back. Usually this happens within the first 2 to 5 years after the initial treatment, but it may take more than a decade.

Even metastatic parathyroid cancer (cancer that has spread to other areas) tends to be slow growing. Overall, almost 60% of patients survive for at least 5 years after their parathyroid cancer is diagnosed, and half or more may survive for at least 10 years. The average survival time after the diagnosis of parathyroid cancer is 6 to 7 years.

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