Chronic Lymphocytic Thyroiditis May Limit the Utility of Molecular Testing in AUS/FLUS Thyroid Nodules

Introduction: Chronic lymphocytic thyroiditis (CLT) may increase the likelihood of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) results in thyroid nodules by fine needle aspiration (FNA). Gene expression classifier (GEC) and Thyroid Sequencing (ThyroSeq) may better stratify rate of malignancy (ROM) of AUS/FLUS thyroid nodules. This study compares the utility of molecular tests in determining malignancy in surgical patients with concomitant AUS/FLUS thyroid nodules and CLT. Methods: A retrospective review of 1648 patients with index thyroid nodules who underwent FNA and thyroidectomy at a single institution was performed. Patients with concomitant AUS/FLUS thyroid nodules and CLT were subdivided into three diagnostic groups: FNA only, FNA with GEC, and FNA with ThyroSeq. Patients with AUS/FLUS thyroid nodules without CLT were subdivided into similar groups. Final histopathology of the cohorts was further stratified into benignity and malignancy and analyzed using Chi-squared statistics. Results: Of 463 study patients, 86 had concomitant AUS/FLUS thyroid nodules and CLT with a 52% ROM, and the difference of ROM among FNA only (48%), suspicious GEC (50%), or positive ThyroSeq (69%) was not significant. In 377 patients with AUS/FLUS thyroid nodules without CL, ROM was 59%. ROM among these patients was significantly higher when molecular testing was used (FNA only 51%, suspicious GEC 65%, and positive ThyroSeq 68%; P < 0.05). Conclusions: Molecular tests may have limited value in predicting malignancy in surgical patients with concomitant AUS/FLUS thyroid nodules and CLT. (C) 2023 Elsevier Inc. All rights reserved.