Primary parathyroid hyperplasia of water-clear cell type. Transformation of water-clear cells into chief cells.

An exceptional case of water-clear cell hyperplasia (WCCH) of the parathyroid glands is presented. Parathyroid tissue was excised at three operations during a period of twenty years before the patient eventually became normocalcemic. Microscopic evaluation of the parathyroids from the first operation showed typical WCCH-findings. However, the parathyroid tissue excised at the last operation was composed of chief cells. There were calcifications and even bone formation. A pigment with the staining and electron-microscopic characteristics of lipofuscin was found in abundance. There were also a few oxyphils. This case shows that clear cells, originally derived from chief cells, can transform into chief cells again.