Background: One reason postulated for the increase in the incidence of differentiated thyroid cancer is the liberal use of imaging modalities. Thyroid nodules are being detected more frequently and are often biopsied independent of imaging characteristics. Though the majority of nodules biopsied are benign, 8-16% turn out to be cytologically indeterminate nodules traditionally requiring at least a diagnostic thyroid lobectomy. The AFIRMA GEC test has been reported to help reduce the need for diagnostic thyroid lobectomy when reported benign. A suspicious for malignancy diagnosis carries a 40-50% risk of malignancy. We elected to review our experience with the AFIRMA GEC when it was read as suspicious for malignancy, though our in-house cytopathology review was benign, in order to help inform patients about their risk of malignancy in this situation.
Methods: Following Institutional Review Board approval, all patients who had a thyroid fine needle aspiration cytology that was reported as an AFIRMA suspicious for malignancy result by Veracyte between 2012 and 2018 were reviewed. Since all outside thyroid cytopathology is reviewed in house before surgery, those that were read as benign by our cytopthologists were then correlated with final excisional surgical pathology.
Results: 30 patients had an AFIRMA suspicious result that was read by our in-house cytopathologists as benign. Of these,15 patients underwent surgery . Of the patients that underwent surgery more than 60% of the patients were women. Most of the thyroid nodules in the study (88%) were less than 4 cm. All patients had an AFIRMA suspicious read and 9 patients(60%) underwent a thyroid lobectomy and 6 patients(60%) underwent total thyroidectomy. None of the patients experienced complications related to the surgery.
14/17 of the index nodules FNA biopsied with an AFIRMA GEC suspicious for malignancy result (82%) were benign on final histopathology. 3/17 turned out to be low risk differentiated thyroid cancer.
Conclusion: A tertiary care center with a high volume of thyroid cytopathology review is more accurate at predicting benign thyroid nodules than the Afirma GEC at predicting malignancy when reported as suspicious. Only low risk DTC was identified in the three index nodules that were incorrectly read as benign on in house cytology. Expert cytopathology review should be performed when the Afrima GEC is suspicious for malignancy and when its benign. The information should be used to help support active surveillance and thyroid lobectomy alone when clinically indicated.