Parathyroid cancer is a rare disease in which malignant (cancer) cells form in the tissues of a parathyroid gland.

The parathyroid glands are four pea-sized organs found in the neck near the thyroid gland. The parathyroid glands make parathyroid hormone (PTH or parathormone). PTH helps the body use and store calcium to keep the calcium in the blood at normal levels.

A parathyroid gland may become overactive and make too much PTH, a condition called hyperparathyroidism. Hyperparathyroidism can occur when a benign tumor (noncancer), called an adenoma, forms on one of the parathyroid glands, and causes it to grow and become overactive. Sometimes hyperparathyroidism can be caused by parathyroid cancer, but this is very rare.

The extra PTH causes:

• The calcium stored in the bones to move into the blood.
• The intestines to absorb more calcium from the food we eat.

This condition is called hypercalcemia (too much calcium in the blood).

The hypercalcemia caused by hyperparathyroidism is more serious and life-threatening than parathyroid cancer itself and treating hypercalcemia is as important as treating the cancer.

Having certain inherited disorders can increase the risk of developing parathyroid cancer.

Anything that increases the chance of getting a disease is called a risk factor. Risk factors for parathyroid cancer include the following rare disorders that are inherited (passed down from parent to child):

• Familial isolated hyperparathyroidism (FIHP).
• Multiple endocrine neoplasia type 1 (MEN1) syndrome.

Treatment with radiation therapy may increase the risk of developing a parathyroid adenoma.

Signs and symptoms of parathyroid cancer include weakness, feeling tired, and a lump in the neck.

Most parathyroid cancer signs and symptoms are caused by the hypercalcemia that develops. Signs and symptoms of hypercalcemia include the following:

• Weakness.
• Feeling very tired.
• Nausea and vomiting.
• Loss of appetite.
• Weight loss for no known reason.
• Being much more thirsty than usual.
• Urinating much more than usual.
• Constipation.
• Trouble thinking clearly.

Other signs and symptoms of parathyroid cancer include the following:

• Pain in the abdomen, side, or back that doesn't go away.
• Pain in the bones.
• A broken bone.
• A lump in the neck.
• Change in voice such as hoarseness.
• Trouble swallowing.

Other conditions may cause the same signs and symptoms as parathyroid cancer. Check with your doctor if you have any of these problems.

Tests that examine the neck and blood are used to diagnose parathyroid cancer.

Once blood tests are done and hyperparathyroidism is diagnosed, imaging tests may be done to help find which of the parathyroid glands is overactive. Sometimes the parathyroid glands are hard to find and imaging tests are done to find exactly where they are.

Parathyroid cancer may be hard to diagnose because the cells of a benign parathyroid adenoma and a malignant parathyroid cancer look alike. The patient's symptoms, blood levels of calcium and parathyroid hormone, and characteristics of the tumor are also used to make a diagnosis.

The following tests and procedures may be used:

• Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease. To diagnose parathyroid cancer, the sample of blood is checked for its calcium level.
• Parathyroid hormone test: A procedure in which a blood sample is checked to measure the amount of parathyroid hormone released into the blood by the parathyroid glands. A higher than normal amount of parathyroid hormone can be a sign of disease.
• Sestamibi scan: A type of radionuclide scan used to find an overactive parathyroid gland. A very small amount of a radioactive substance called technetium 99 is injected into a vein and travels through the bloodstream to the parathyroid gland. The radioactive substance will collect in the overactive gland and show up brightly on a special camera that detects radioactivity.
• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
• SPECT scan (single photon emission computed tomography scan): A procedure to find malignant tumor cells in the neck. A small amount of a radioactive substance is injected into a vein or inhaled through the nose. As the substance travels through the blood, a camera rotates around the body and takes pictures of the neck. A computer uses the pictures to make a 3-dimensional (3-D) image of the neck. There will be increased blood flow and more activity in areas where cancer cells are growing. These areas will show up brighter in the picture.
• Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
• Angiogram: A procedure to look at blood vessels and the flow of blood. A contrast dye is injected into the blood vessel. As the contrast dye moves through the blood vessel, x-rays are taken to see if there are any blockages.
• Venous sampling: A procedure in which a sample of blood is taken from specific veins and checked to measure the amounts of certain substances released into the blood by nearby organs and tissues. If imaging tests do not show which parathyroid gland is overactive, blood samples may be taken from veins near each parathyroid gland to find which one is making too much PTH.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis and treatment options depend on the following:

• Whether the calcium level in the blood can be controlled.
• The stage of the cancer.
• Whether the tumor and the capsule around the tumor can be completely removed by surgery.
• The patient's general health.