LAUSR

PAX8 and NKX2.1, indicating absence of thyroid follicle lining cells. None of these parathyroid specimens manifest common somatic mutations seen in thyroid neoplasia. miR expression profiling, using criteria applied to thyroid follicular neoplasia, would have indicated thyroid malignancy if inappropriately assumed to be thyroid. Specific relative miR expression levels differentiated each of the parathyroid states. Normal parathyroid underexpressed miR138. PH underexpressed miR31, 204, and 551. PA overexpressed miR29b, 146, and 375. PC showed hyperexpression of miR31, 204, and 551. Conclusion: Parathyroid lesion can confound FNA cytology diagnosis of nodules presumed to be of thyroid origin. In this initial study ancillary molecular testing can affirm parathyroid tissue origin (messenger RNA expression) and miR expression profiling appears capable of differentiating between parathyroid disease states supporting further confirmatory studies. The approach is effective on fixative-treated specimens.