Serum IgG4 level for malignancy prediction in indeterminate thyroid nodules among patients with or without autoimmune...

The incidence of thyroid nodules (TNs) has increased nowadays, and it is critical to properly differentiate between malignant and benign nodules to prevent unneeded thyroidectomy as well as complications related to surgery. IgG4 significantly contributes to various cancer-associated processes. The present study aimed to assess the value of serum IgG4 level in predicting malignancies in indeterminate thyroid nodules (ITN) among patients with and without autoimmune thyroid disease (AITD). A total of 67 patients with indeterminate cytology thyroid nodules (Bethesda III and IV, according to Bethesda system for reporting thyroid cytopathology) were selected. Preoperative serum thyroid profile, IgG4, anti-thyroglobulin (TG) and anti-thyroid peroxidase (TPO) antibody levels were determined. After total thyroidectomy, patients were categorized based on the postoperative histopathology outcome into two groups. Group (I): confirmed benign nodules (n=55) and Group (II): confirmed malignant TNs (n=12). IgG4 levels were significantly elevated among malignant TNs patients than in benign TNs patients, with a median (IQR) of 194.5 mg/dl (183 - 214) vs. 91 mg/dl (60 - 113), respectively (P=0.001). The cut-off value for differentiation between malignant and benign TNs was >180 mg/dl with a sensitivity of 75% and specificity of 100%. There was a significant positive correlation between thyroid antibodies and IgG4 levels (P=0.001). AITD patients had significantly higher level of IgG4 compared with those without AITD 189 mg/dl (153 - 208) vs 89 mg/dl (58 - 112), respectively (P =0.001). Eighty percent (12/15) of patients with AITD had malignant TNs with IgG4 >180 mg/dl, while 20% (3/15) of patients with benign TNs showed IgG4 levels < 180 mg/dl. In conclusion, IgG4 level can be proposed as a predictor of malignant TNs.