Abstract

We report two cases of hyalinizing trabecular carcinoma (HTC) of the thyroid gland. These two patients were euthyroid women aged 36 and 65 years of age. The tumors were encapsulated and measured 0.8 and 4.0 cm in diameter, respectively. Histologically, the tumors were composed of a compact proliferation of cells in a lobular and trabecular pattern with an intervening hyalinized, fibrotic vascular stroma. Occasionally the cells were arrayed in microfollicles. Multiple and serial sections showed cords of tumor cells invading into the capsule in both cases and vascular invasion in one case. These findings suggested that HTCs are a malignant counterpart of hyalinizing trabecular adenoma, similar to conventional follicular tumor. Positive immunostaining of tumor cells for thyroglobulin and negative staining for high molecular weight cytokeratin, cytokeratin 19, neuron specific enolase, chromogranin, and synaptophysin allowed distinction from medullary carcinoma. Even though HTCs are an heterogeneous group of tumors, the present two cases are probably variants of follicular carcinoma rather than papillary carcinoma.

• Keywords: Hyalinizing trabecular carcinoma;Thyroid;