Reduced HBME-1 immunoreactivity of papillary thyroid carcinoma and papillary thyroid carcinoma-related neoplastic lesions with Hurthle cell and/or, apocrine-like changes

Background: We have recently observed that Hurthle cell tumours and papillary thyroid carcinoma with tumour cells showing decapitation of luminal portion of the cytoplasm (apocrine-like changes) display negative or decreased immunoreactivity for HBME. The purpose of this study is to correlate papillary thyroid carcinoma with positive and negative immunoreactivity for HBME with the histopathological features. Methods and results: Two hundred and five thyroid neoplasms including carcinoma and adenomas were grouped into Hurthle cell tumours, tumours with or without some features of Hurthle cells, tumours with apocrine-like changes and adenomas with or without limited nuclear features of papillary thyroid carcinoma but not diagnostic for papillary thyroid carcinoma. All neoplasms were submitted for immunostaining with cytokeratin 19 (CK19) and HBME. Papillary thyroid carcinoma. follicular carcinoma and follicular adenoma that have areas of limited nuclear features but riot diagnostic for papillary thyroid carcinoma showed immunostaining for HBME than their respective counterparts with Hurthle cell changes. All Hurthle cell tumours showed negative to focal reactivity. This decrease of reactivity for HBME was proportional to the levels of Hurthle cell changes. In addition, focal to extensive apocrine-like changes were seen in most Hurthle cell neoplasms and rarely seen in non-Hurthle cell neoplasms. Apocrine-like changes abolished or decreased HBME immunoreactivity of papillary thyroid carcinoma and tumours with limited nuclear features. Immunostaining for cytokeratin AE3 was not affected by Hurthle cell or apocrine-like changes. Conclusions: All papillary thyroid carcinomas without Hurthle cell or apocrine-like differentiation are reactive for HBME. Hurthle cell tumours and tumours with Hurthle cell or apocrine-like changes show negative or focal reactivity for HBME. Except for this limitation, HBME is a sensitive marker for papillary thyroid carcinoma and tumours with limited nuclear features.