Contributor: Gordon K. Klintworth
Hyperplasia of the parathyroid gland may involve the  chief cells or clear cells of the parathyroid gland. The vast majority of individuals with primary hyperparathyroidism [hyperparathyroidism - primary] have a parathyroid adenoma [adenoma - parathyroid gland] (80-85%) or chief cell hyperplasia (15-20%). Chief cell hyperplasia needs to be differentiated from an adenoma of the parathyroid gland. This is not possible from a gross examination of a single parathyroid gland or by an examination using light or transmission electron microscopy. The diagnosis of an adenoma of the parathyroid gland requires the finding of normal parathyoid tissue in an uninvolved parathyroid gland.