Parathyroid Carcinoma Revisited: Clinical and Pathological Insights From Two Decades of Experience

BACKGROUND: Parathyroid carcinoma is a rare endocrine malignancy (< 1% of primary hyperparathyroidism and 0.005% of all cancers) that often mimics a benign adenoma, leading to diagnosis only after surgery, unless invasion or metastasis is present. OBJECTIVE: To identify distinguishing clinical, biochemical and pathological features of parathyroid carcinoma in comparison with primary parathyroid adenoma and atypical parathyroid tumor and to determine its perioperative predictors. METHODS: A retrospective analysis compared 16 histopathologically confirmed parathyroid carcinoma cases with 378 primary parathyroid adenoma and 11 atypical parathyroid tumors, evaluating and contrasting their clinical and laboratory features. RESULTS: No significant differences in age or gender were observed across groups. Parathyroid carcinoma was significantly associated with hoarseness, hypercalcaemic crisis, palpable neck mass (all p < 0.001), pancreatitis, and concomitant bone/kidney involvement (both p < 0.05). Ridge-penalized logistic regression identified hoarseness, palpable neck mass and an involved parathyroid gland weight ≥ 3 grams (g) as significant perioperative predictors of parathyroid carcinoma while adenoma diameter, serum calcium levels and intact parathyroid hormone (iPTH) were not statistically significant. ROC analysis showed parathyroid adenoma weight of ≥ 7.5 g had the highest diagnostic accuracy (75% sensitivity, 86% specificity), whereas serum calcium and iPTH exhibited only moderate diagnostic performance. Recurrence was observed in 31% of cases. CONCLUSION: Parathyroid carcinoma exhibits more severe clinical and biochemical features and greater gland weight than benign lesions. The high recurrence rate necessitates rigorous long-term surveillance. While offering a framework for preoperative risk stratification, these retrospective findings require prospective validation in larger cohorts.