Immunohistochemical analysis of thyroid adenomas with Hurthle cells

Twenty-five cases of thyroid adenomas with Hurthle cell changes, both pure and focal, were studied histologically and immunohistochemically with two objectives: first to elucidate the relationship between the normal uninvolved thyroid and the adenoma; and second, to evaluate the role of immunohistochemical studies in adenomas with Hurthle cell changes. Representative sections were stained with a panel of nine antibodies directed against thyroglobulin (TG), high molecular weight keratin (HMK), low molecular weight keratin (LMK), p53, bcl-2, epithelial membrane antigen (EMA), S100, carcinoembryonic antigen (CEA) and HMB45. In all cases, uniform strong positive staining (+3) with TG and bcl-2 was seen in the normal thyroid tissue while the adenoma stained moderately positive (+2). The reverse pattern was observed with LMK staining. Non-adenomatous thyroid cells were p53-negative, the majority of the Hurthle cells, however, were p53-positive and adenomas with an increased number of Hurthle cells had an increased percentage of p53 staining. The expression of EMA was variable. All thyroid cells both outside and within the adenoma were S100-, CEA-4 and HMB45-negative in all cases. The exact significance of p53 overexpression in the Hurthle cells needs further evaluation.