Emerin immunohistochemistry reveals diagnostic features of nuclear membrane arrangement in thyroid lesions

Objective appreciation of irregularities of the nuclear shape is a key parameter in the diagnosis of thyroid lesions, since foldings of the nuclear membrane (NM) featuring indentations, grooves and pseudoinclusions characterize papillary thyroid carcinomas (PTC). The aim was to focus on the immunohistochemistry of emerin, a protein of the NM whose decoration best demarcates the nuclear shape. Immunohistochemistry of the NM with emerin as well as three-dimensional reconstruction of the images (through deconvolution processing) performed on a series of 54 cases (processed following the tissue array procedure) revealed a uniform arrangement of the NM in non-neoplastic lesions (thyroiditis, microfollicular goitre, follicular adenoma) and normal thyroid as well as in follicular carcinoma. In contrast, irregular folding of the membrane and presence of curling and invaginations, eventually leading to the formation of nuclear pseudoinclusions, was observed in PTC cells. Decoration of the NM represents an original approach to identify PTC nuclear shape, highlights new structural features and might be helpful in the differential diagnosis between so-called nuclear pseudoinclusions and artefactual 'bubbles'.