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. Here, CGA is linked to parathyroid gland carcinoma.