Neuroendocrine differentiation in hyalinizing trabecular tumor of the thyroid

Abstract

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.

Hyalinizing trabecular tumor of the thyroid displaying neuroendocrine differentiation

“…We agree with the authors' assumption that their finding suggests HTT can differentiate into both follicular cells and neuroendocrine cells [3].…”

“…The prevalence of such dual differentiation in HTT is not known, but it is likely to be more frequent than suspected by Shikama and colleagues, who claimed that "In the world literature to date, only two cases of HTT with endocrine cells, including the current case, have been reported" [3]. Shikama and colleagues did not take into account the two cases reported by our group [1,2].…”

“…Dear Sir, Shikama and colleagues [3] reported recently an interesting case of a hyalinizing trabecular tumor of the thyroid (HTT) displaying neuroendocrine differentiation. We agree with the authors' assumption that their finding suggests HTT can differentiate into both follicular cells and neuroendocrine cells [3].…”

Histopathology of Thyroid Tumors. An Overview

“…Reand paraganglioma-like adenoma of the thyroid, may be related to papillary carcinoma at the molecular level 4,5 , while others propose a multidirectional differentiation from pluripotent primitive cells 6 . Some of these controversial issues are challenged by Lloyd 7 who concludes that additional studies are needed to clearly define this entity.…”

“…Poorly differentiated thyroid carcinoma represents a heterogeneous group of malignant neoplasms, with various histologic patterns of growth and different biologic behavior, that lie somewhere between welldifferentiated and undifferentiated carcinomas 6,[31][32][33] . The heterogeneity of these tumors reflects the different terms used to describe and diagnose this entity, including solid, trabecular, insular, poorly differentiated, intermediate type, less well-differentiated and follicular carcinoma with insular component 2,[32][33][34][35] .…”