Irradiation as an etiologic factor in tumours of the thyroid, parathyroid and salivary glands.

Irradiation to the head and neck region, usually of low dosage, results in an increased frequency of thyroid, parathyroid and salivary gland tumours. The authors have reviewed their experience with these tumours. Fifty of 475 patients with carcinoma of the thyroid had received previous irradiation. Papillary or mixed papillar-follicular carcinoma occurred most commonly. Eleven of 100 patients with primary hyperparathyroidism had been irradiated and had a parathyroid adenoma. Twenty of 662 patients with salivary gland tumours had previously been irradiated. Mucoepidermoid carcinoma was the most common tumour. Patients who have been irradiated and have a palpable abnormality of the thyroid or the salivary glands should be treated surgically. The various noninvasive tests are of little value in distinguishing between a benign and a malignant tumour. Those with hypercalcemia, considered to be due to primary hyperparathyroidism, should be treated by exploration of the neck, identification of the four parathyroid glands and excision of an adenoma with biopsy of the three remaining glands. If more than one gland is abnormal, a subtotal parathyroidectomy is recommended.