Cystic parathyroid gland hyperplasia--hyperparathyroidism presenting as a neck mass.

Hyperparathyroidism may occasionally present as a neck mass resulting from cystic change in a parathyroid adenoma. We report an unusual instance of hyperparathyroidism presenting as a palpable, but asymptomatic hyperplastic parathyroid gland cyst. We conclude that hyperplastic parathyroid glands may undergo cystic degeneration resulting in a palpable neck mass; and that all functional parathyroid gland cysts are not necessarily adenomas. Therefore, during parathyroidectomy procedures, biopsy material from at least one additional parathyroid gland should be obtained.