Higher magnification of a parathyroid adenoma showing sheets of cells with an appearance intermediate between chief cells and oxyphil cells. There is nuclear hyperchromasia and some variation in the nuclear size. The distinction of a parathyroid adenoma from chief cell hyperplasia can be extremely challenging. If the remainder of the parathyroid glands have normal or atrophied appearance, it supports the diagnosis of a parathyroid adenoma in a given lesion. Technetium-99m radionuclide scan will show increased uptake in one of the glands in a case of adenoma, whereas more than one gland would demonstrate increased uptake in parathyroid hyperplasia.