Cancer-derived Immunoglobulin G: A Novel Marker for Differential Diagnosis and Relapse Prediction in Parathyroid Carcinoma.

Objective A differential diagnosis between malignant and benign parathyroid lesions is difficult due to their overlapping clinicopathological characteristics. As such, molecular markers are urgently needed. Cancer-derived immunoglobulin G (CIgG) is a novel molecule playing important roles in carcinogenesis. The present study aimed to investigate the clinical significance of CIgG in parathyroid neoplasms. Patients Fifty patients with parathyroid carcinoma (PC), 50 patients with parathyroid adenoma (PA) and 9 patients with parathyroid hyperplasia (PH) were retrospectively enrolled in the current study. Measurements Immunohistochemistry was used to assess CIgG expression in these patients. The performance of CIgG expression in the differential diagnosis between parathyroid lesions was assessed by receiver operating characteristic (ROC) curves. The associations between CIgG expression and clinical outcomes were also analysed by Kaplan-Meier survival curves and Cox proportional hazards models. Results The expression level of CIgG was significantly higher in PC patients than in PA or PH patients (P < .001). CIgG expression discriminated PC from PA or PH, with an area under the ROC curve of 0.84 (76% sensitivity and 88% specificity). High CIgG expression was significantly associated with worse disease-free survival (DFS) in PC patients (P = .018) and was validated as an independent risk factor for DFS in the multivariable Cox regression analysis (P = .002). Conclusions The ability of CIgG expression both in the differential diagnosis between malignant and benign parathyroid lesions and in the prognosis prediction for PC was shown in the present study. CIgG might be used as a novel biomarker of parathyroid lesions in future clinical practice.