Pathology of parathyroid carcinoma. (a) Gross pathology of parathyroid carcinoma. A large solid tan mass (left, P) was adhered to the right lobe of thyroid gland (right, T). (b) Histopathology demonstrated vascular invasion (arrow) in the tumor capsule (H&E, 40x). (c) The tumor composed mixture of chief cells and oncocytic cells types arranged in solid sheets trabecular and nest pattern (H&E, 200x). (d) Immunohistochemical study for parathyroid hormone (PTH) revealed immunoreactivity in the tumor cells (PTH, 400x).