IHC was positive for chromogranin, synaptophysin, and S-100 and negative forcalcitonin in all five thyroid paragangliomas, whereas the three excluded candidate tumors stained positive for pan-cytokeratin, a marker excluding endocrine tumors.
We provide a classifying rule for differential diagnosis that combines negativity or low staining for calcitonin gene-related protein (histologic score, <10) or calcitonin (histologic score, <50) together with positivity of any of NADH dehydrogenase 1 alpha subcomplex, 4-like 2; cytochrome c oxidase subunit IV isoform 2; or vesicular monoamine transporter 2 to predict paragangliomas, showing a prediction error of 0%.