THE INFLUENCE OF SURGICAL EXTENT AND PARAFIBROMIN STAINING ON THE OUTCOME OF PARATHYROID CARCINOMA: 20-YEAR EXPERIENCE FROM A SINGLE INSTITUTE.

Objective: Parathyroid carcinoma (PC) is a rare endocrine malignancy with a poor prognosis. The optimal surgical procedure and prognostic factors for PC remain controversial. Methods: Clinical information and parafibromin staining results from 53 patients with PC were reviewed retrospectively from 1997 to 2018. Immunohistochemical staining for parafibromin was performed on formalin-fixed, paraffin-embedded tissue samples. The influence of clinical parameters, surgical procedure, and parafibromin staining of tumor tissues on prognosis were evaluated. Results: A total of 53 patients with PC were enrolled in this study. The male to female ratio was 1.94:1. En bloc resection was performed as initial surgery for 18 patients (34.0%), and 35 patients (66.0%) underwent local resection. Parafibromin staining was negative in the tumor tissues of 24 PC patients (45.3%). Thirty-three patients suffered from local recurrence or distant metastasis, and overall mortality was 16/53 at a median follow-up time of 80 months (range, 7 to 282 months). Cox proportional hazards analysis showed that negative parafibromin staining (hazard ratio [HR], 4.13; 95% confidence interval [CI], 1.73 to 9.87; P = .001) was related to recurrence or metastasis and that age >50 years (HR, 5.66; 95% CI, 1.58 to 20.31; P = .008) was related to mortality. The extent of resection was not related to recurrence or overall survival. Conclusion: The majority of PC patients have a relatively long survival with multiple recurrences. Absence of parafibromin staining was a factor that influenced PC recurrence. The main factor influencing PC outcomes may be the biological characteristics rather than surgical extent. Abbreviations: CI = confidence interval; DFS = disease-free survival; HR = hazard ratio; OS = overall survival; PC = parathyroid carcinoma; WHO = World Health Organization.