PTH and parathyroid gland carcinoma: Immunohistochemistry staining showed significantly increased expression of CgA, PTH, and Syn in 3 patients, suggesting differentiated parathyroid adenocarcinoma, which further confirmed parathyroid carcinoma is a rare endocrine tumor, CgA, PTH, and Syn may served as specific marker of parathyroid carcinoma, serum CgA and PTH may be circulating markers.