Parathyroid carcinoma is a rare cancer resulting in parathyroid adenoma to carcinoma progression. It forms in tissues of one or more of the parathyroid glands (four pea-sized glands in the neck that make parathyroid hormone (PTH). PTH helps the body maintain normal levels of serum calcium by promoting calcium reabsorption from bone. It is antagonized by the hormone calcitonin, which prompts calcium storage.). It is rare, with documented cases of less than one thousand since its first discovery in 1904; and much less common than parathyroid adenoma. It can be difficult to excise. The rate of occurrence of parathyroid carcinoma is between 0.5% to 5%

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Wiki: Parathyroid carcinoma