Preoperative Serum Thyroglobulin as an Adjunct to Fine-Needle Aspiration in Predicting Well-Differentiated Thyroid Cancer

Background/Purpose: When fine-needle aspiration biopsy (FNAB) of a thyroid nodule yields indeterminate pathology, management decisions become complex, and other preoperative predictors of thyroid cancer must be employed to assess the risk of malignancy. Although thyroglobulin (Tg) is currently accepted as the serum marker of choice in the detection of well-differentiated thyroid cancer (WDTC) recurrence, its preoperative role in the workup of a thyroid nodule remains controversial. The purpose of this study was to evaluate the potential role for Tg as a preoperative indicator of primary WDTC, specifically in patients with indeterminate FNAB. Methods: This was a retrospective review of 861 consecutive thyroidectomy patients; 297 patients had indeterminate FNAB, of which 68 had serum levels of Tg measured prior to surgery. The predictive value of various threshold levels of preoperative Tg for WDTC was evaluated. Patients with nonindeterminate FNAB or final pathology containing medullary carcinoma, anaplastic carcinoma, or lymphoma were excluded. Results: Eighty-one percent (25 of 31) of patients with both indeterminate FNAB and preoperative Tg >= 75 mu g/L had well-differentiated cancer on final pathology compared to 58% (172 of 297) of patients with indeterminate cytology alone (p = .014, RR = 1.4). In addition, mean preoperative Tg levels were found to be significantly higher in patients with WDTC compared to those with benign pathology (223 vs 53 mu g/L, p = .007). Discussion/Conclusion: Our results imply that elevated preoperative serum Tg levels may be predictive of WDTC. This marker may be useful as an aid when making management decisions in patients with indeterminate cytology.