Parathyroid adenomas following irradiation.

Parathyroid adenomas have been demonstrated to occur following external head and neck irradiation. The median latency interval is 30 years. In a series of 74 consecutive patients with histologically diagnosed parathyroid adenomas, 25% gave a history of prior radiation exposure. When compared to a matched control incidence of 7.9%, statistical significance is reached at p less than 0.01. Thyroid abnormalities were present in 68% of the irradiated patients, and 30% of these were malignant. Tumor of skin, breast, and parotid gland also occurrred more frequently than expected. Forty-seven percent of the irradiated group had malignant neoplasms within the radiation field. The histopathology of the radiation-associated parathyroid adenomas is similar to that seen experimentally.