Fig. 4

The left superior parathyroid adenoma showed cystic characteristics in the central region, and the peripheral region of the lesion was surrounded by parathyroid parenchyma (a: HE-stained, magnification × 50; inset; × 200). HE staining revealed that the encapsulated IPA was composed of chief cells surrounded by a rim of normal thyroid tissue, which can be seen in the upper right portion of the slide (b: HE-stained, magnification × 50; inset; × 200). Immunohistochemical staining of the IPA for chromogranin A (c) and synaptophysin (d) were positive