Thyroid lymphoepithelial nodule.

Thyroid benign lymphoepithelial lesions are rare in adults, reported as associated with thyroiditis or adjacent to tumours. Here we report a unique case of a thyroid solid nodule with benign lymphoepithelial morphology. A 56-year-old woman presented with a thyroid nodule increasing in size. Thyroid function was normal. On the surgical resection specimen, in addition to a 2-cm follicular adenoma, there was, at distance, a 0.5-cm solid nodule with lymphoepithelial morphology, without Hassal's corpuscles or calcifications. On immunohistochemistry, the epithelial component was cytokeratin 5/6 positive and very focally cytokeratin 7 positive, the immunophenotype of the lymphoid tissue confirming the benign nature. The diagnosis of thyroid benign lymphoepithelial nodule was proposed. In conclusion, recognition of thyroid solid benign lymphoepithelial nodules is important since they can be misdiagnosed with other thyroid micronodule types including carcinoma, primary or metastatic.