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.
Anatomy of the thyroid and parathyroid glands. The thyroid gland lies at the base of the throat near the trachea. It is shaped like a butterfly, with the right lobe and left lobe connected by a thin piece of tissue called the isthmus. The parathyroid glands are four pea-sized organs found in the neck near the thyroid. The thyroid and parathyroid glands make hormones.
A parathyroid gland may become overactive and make too much PTH, a condition called hyperparathyroidism. Hyperparathyroidism can occur when a benign tumour (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.
Possible signs of parathyroid cancer include weakness, feeling tired, and a lump in the neck.
Most parathyroid cancer symptoms are caused by the hypercalcemia that develops. Symptoms of hypercalcemia include the following:
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.
Trouble thinking clearly.
Other 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.
Other conditions may cause the same symptoms as parathyroid cancer. A doctor should be consulted if any of these problems occur.
Parathyroid carcinoma is a rare malignancy of the parathyroid glands. These tumours usually secrete parathyroid hormone, thereby producing hyperparathyroidism, which is usually severe. Parathyroid carcinoma may be suspected, but it usually cannot be confirmed prior to operation. This complicates the treatment strategy.
Parathyroid carcinoma causes hyperparathyroidism (for a more complete discussion see Hyperparathyroidism) in all but a few rare cases of nonfunctional parathyroid carcinoma. Hyperparathyroidism is caused by overproduction of parathyroid hormone. In most cases, hyperparathyroidism is caused by a single benign adenoma (approximately 85%). The vast majority of the remaining cases are caused by parathyroid hyperplasia or multiple adenomas. In less than 1% of cases of hyperparathyroidism, the etiology is parathyroid carcinoma.
The hyperparathyroidism seen in parathyroid carcinoma is usually severe, with high serum calcium levels, severe bone disease, and renal stones. Rarely, parathyroid cancer can be nonfunctional, that is, it may cause a tumour but not produce parathyroid hormone and the sequelae of hyperparathyroidism. Overproduction of authentic parathyroid hormone from nonparathyroid sources is extremely rare but has been reported. Modern assays for parathyroid hormone measure the intact, authentic molecule and do not detect similar molecules produced by other tumours. Therefore, an elevated parathyroid hormone level is virtually always parathyroid in origin.
Untreated, parathyroid carcinoma leads to severe symptoms of hyperparathyroidism and may cause renal stones, nephrocalcinosis, pathologic fractures, and neuropsychiatric symptoms. The diagnosis is often not made prior to parathyroidectomy. This results in inadequate tumour excision and a propensity to local recurrence. Regional lymph node and distant metastases are usually not present at initial diagnosis. Recurrences may be treated by local excision or ablative treatments such as radiofrequency ablation. Death is usually caused by medically refractory hypercalcemia and seldom tumour burden alone.
Tests that examine the neck and blood are used to detect (find) and 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 tumour are also used to make a diagnosis.
The following tests and procedures may be used:
- Physical exam and 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 in the organ or tissue that makes it. 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 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.
- 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 (chance of recovery) and treatment options depend on the following:
Whether the calcium level in the blood can be controlled.
The stage of the cancer.
Whether the tumour and the capsule around the tumour can be completely removed by surgery.
- The patient's general health.
For more information on Parathyroid Cancer click here
This link is to the National Cancer Institute (NCI) cancer website in the United States. There may be references to drugs and clinical trials that are not available here in Australia.
Information has also been sourced from emedicine.medscape.com