The rapid identification of "normal" parathyroid glands by the presence of intracellular fat.

Staining of frozen sections of small parathyroid biopsies from patients with primary hyperparathyroidism with Sudan II or IV revealed the almost uniform presence of numerous prominent intracellular sudanophilic bodies in the chief cells of suppressed "normal" parathyroid glands. These sudanophilic bodies were generally absent from the abnormal chief cells of parathyroid adenomas and chief cell hyperplasias. This difference in intracellular lipid provides a rapid, reliable, and easy method for distinguishing at the time of parathyroid exploration between an adenoma which is always accompanied by "normal" parathyroid glands and a chief cell hyperplasia in which all of the glands are abnormal.