Tumor size rather than the thyroid invasion affects the prognosis of parathyroid carcinoma without lymph node or distant metastasis

Purpose This study aimed to explore the prognostic value of thyroid invasion of parathyroid carcinoma without lymph node or distant metastasis. Methods Two hundred and nine cases of parathyroid carcinoma from the SEER (1989-2014) were eligible for this study. A Chi-squared test, t test, X-tile, Kaplan-Meier curves, and multivariate Cox proportional hazard regression were used for analysis. Results Thyroid invasion, sex, race, age, radiation, and surgery were not significantly associated with cancer-specific survival by multivariate analysis. However, tumor size >= 4 cm was significantly associated with worse cancer-specific survival (P < 0.001). Conclusion Thyroid invasion, which was the criterion for T-1 and T-2 staging criteria of parathyroid carcinoma according to the AJCC, did not affect the prognosis of patients with parathyroid carcinoma without local lymph node or distant metastasis. Our study indicates that a tumor size >= 4 cm may be an appropriate indicator of T-1 and T-2 cancer staging.