Parathyroid cancer

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Malignant tumours of the parathyroid gland

Malignant tumours of the parathyroid gland are cancerous growths that have the potential to spread (metastasize) to other parts of the body. Parathyroid carcinoma is a rare, slow-growing (indolent) tumour.

Most parathyroid tumours are functional and produce high and unregulated levels of parathyroid hormone (PTH). The over-production of PTH is called hyperparathyroidism. Less than 1% of primary hyperparathyroidism cases are caused by parathyroid carcinoma. Most cases of hyperparathyroidism are caused by parathyroid adenomas. Hyperparathyroidism leads to high levels of calcium in the blood (hypercalcemia).

Benign and malignant parathyroid tumours may cause similar signs and symptoms. Certain features suggest parathyroid carcinoma, including:

  • blood calcium level greater than 14 mg/dL
  • blood PTH level greater than twice that of normal (can be 3–10 times the normal level)
  • a lump in the neck that can be felt in a person with hypercalcemia
  • vocal cord paralysis in a person with hypercalcemia
  • kidney and bone disease seen in a person with an increased PTH level in the blood

Parathyroid carcinoma is not identified with a biopsy due to the fear of tumour seeding (spreading the cancer).

Parathyroid carcinomas and adenomas (benign tumours) often look different. Malignant parathyroid tumours are usually identified during surgery based on their appearance. This is usually the most important point in proper diagnosis and treatment of parathyroid cancer.

Parathyroid carcinoma (malignant tumour)Parathyroid adenoma (benign tumour)

stony or hard consistency

usually soft

often gray-white in colour

red-brown in colour

sphere shaped

oval or round in shape

between 3–3.5 cm in diameter

approximately 1.5 cm in diameter

surrounded by a thick capsule and attached or spread to nearby tissues

unattached and without spread to nearby tissues

Some parathyroid carcinomas look like adenomas, while other tumours sometimes look like parathyroid carcinoma. The diagnosis of parathyroid carcinoma must be confirmed by a pathologist, who examines the tissue using microscopy and special testing.


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