The Diagnostic Utility of CD117 (c-KIT) as Adjunctive Preoperative Marker in Solitary Thyroid Nodule Management

Background: Unfortunately, about 30% of FNAC findings reveal an intermediate or suspicious follicular proliferation followed by thyroid surgery to establish the diagnosis. Therefore, reliable preoperative molecular markers are immensely needed to distinguish benign from malignant thyroid nodules to avoid unnecessary aggressive surgical interference in benign lesions or reoperation in malignant lesions. Aim: To investigate the utility of c-KIT marker in combination with the immunopanel of CD56, Galectin-3 and HBME-1, to distinguish between benign and malignant thyroid lesions on cell blocks in order to reduce unnecessary thyroid surgery. Patients and methods: This study was conducted on 113 patients with solitary thyroid nodule, in Pathology Department and Surgical Oncology Unit at General Surgery Department, Tanta University Hospital from June 2015 to May 2017. After histopathological examination of FNAC samples, Cell blocks were prepared for only cases diagnosed as follicular neoplasm/suspicious for follicular neoplasm for further immunohistochemistry of immunopanel including c-KIT, CD56, Galectin -3 and HBME-1, then the selected cases underwent hemithyroidectomy to establish a histological tissue diagnosis. Results: Thirty six out of 113 patients (31.8%) were diagnosed as follicular neoplasm/suspicious for follicular neoplasm on FNAC. The combined panel of CD56, Galectin-3 and HBME-1 results on cell blocks showed sensitivity 80.0%, specificity 100%, PPV 100.0%, NPV 92.86% and the accuracy was 94.44%. However after the addition of c-KIT to the immunopanel the diagnostic sensitivity, specificity, PPV, NPV and total accuracy improved to 100% for all. Conclusion: The diagnostic preoperative accuracy of the combined CD56, Galectin-3 and HBME-1 panel in solitary thyroid nodules with suspicious cytology could be extremely improved with the addition of c- as a supplementary preoperative immunostain in order to avoid over or under treatment.