Neuroendocrine differentiation in hyalinizing trabecular tumor of the thyroid

The presence of neuroendocrine cells is putative in thyroid hyalinizing trabecular tumor (HTT), although this entity requires a differential diagnosis from paraganglioma or medullary carcinoma of the thyroid, due to similarity of the growth pattern of the cells. Here, we present a case of HTT with a mixture of endocrine cells stained positive for somatostatin, chromogranin A and Grimelius' silver impregnation. The histology and results of other immunostainings were consistent with the features typical for HTT. In the world literature to date, only two cases of HTT with endocrine cells, including the current case, have been reported. Nevertheless, the cases may indicate the diversified differentiation of cells in HTT and may, in part, account for the resemblance of HTT to paraganglioma and medullary carcinoma.