Hyalinizing parathyroid adenoma and hyperplasia: report of 3 cases of an unusual histologic variant.

Fibrosis in the parathyroid glands can be seen in adenomas, in carcinomas, and after fine needle aspiration of the thyroid gland. Fibrosis occurs in approximately 10% of typical adenomas and in all atypical adenomas. This is usually in the form of fibrous bands or trabeculae that intersect the hypercellular parenchyma. However, widespread diffuse fibrosis or sclerosis in either parathyroid gland hyperplasia or adenoma has not been reported before in the English medical literature. We report 3 cases of hyperparathyroidism (2 adenomas and 1 hyperplasia) with an unusual pattern of sclerosis. The hyalinized, eosinophilic fibrous tissue was diffusely distributed within and around the parathyroid parenchyma, often isolating groups of cells and single cells.