Diagnostic significance of parafibromin expression in parathyroid carcinoma

Parathyroid carcinomas are difficult to distinguish from adenomas according to the current diagnostic criteria. The judgment of local infiltration is subjective and inconsistent. Existing studies have found that the CDC73 gene encoding parafibromin is related to the occurrence of parathyroid carcinomas. This study is aimed at investigating whether the immunohistochemistry of parafibromin is helpful in distinguishing malignant from benign parathyroid tumors. A total of 53 patients with parathyroid carcinoma from Peking Union Medical College Hospital were included. Metastasis was found in 17 of 53 patients. In addition, another 53 patients with parathyroid adenomas were included as controls. Appropriate sections were stained with an immunohistochemical autostainer. Three senior pathologists evaluated the sections and analyzed their clinicopathological features independently. The loss of parafibromin expression only occurred in malignant tumors, including all carcinomas with metastasis (17/17) and 14 of 36 carcinomas with only local infiltration. All staining results of adenomas (53/53) were positive. Considering invasion as the gold standard of malignancy, the sensitivity of parafibromin staining is 58%, and the specificity is 100%. If the gold standard is changed to metastasis, the sensitivity becomes 100%, and the specificity becomes 84%. By analyzing clinicopathological features with metastasis and parafibromin staining, it is found that local-infiltrative carcinomas with positive staining results have better biological behaviors than carcinomas that lack parafibromin expression. Parafibromin staining is highly recommended as an auxiliary method in the diagnosis of parathyroid carcinoma.