Lymphoepithelial lesion in the thyroid. A non-specific histological finding.

In order to assess the specificity of lymphoepithelial lesion (LEL) in the diagnosis of thyroid lymphoma, the thyroid glands of patients with Hashimoto's disease, lymphoid infiltrates in the vicinity of papillary carcinoma, focal thyroiditis in Graves' disease and malignant lymphoma of the thyroid were studied by conventional pathological and immunohistochemical techniques using a panel of antibodies against epithelial cells (CAM 5.2) and leucocytes (LCA, pan-T, and pan-B antisera). LEL was encountered in all cases. In cases of peritumoral lymphoid infiltrates LEL represented a focal phenomenon, whereas in Hashimoto's and Graves' diseases and lymphoma, it was found in multiple areas. In cases of malignant lymphoma LEL was encountered in the vicinity of areas where diffuse parenchymal destruction by tumor cells had occurred. The results suggested that although LEL is almost always present in lymphomas it can also be encountered in other diseases of the thyroid. If therefore LEL has no diagnostic specificity, the diagnosis of malignant lymphoma must be supported by other histological findings.