[Thymus-like expression and molecules accessory to division and of thymocyte-stroma interactions in thymomas: a prerequisite for the establishment of an abnormal T-cell repertoire?].

Costimulatory stromal receptors were identified in thymuses and myasthenia gravis (MG)-associated thymic epithelial tumors (TETs) by immunohistochemistry. ICAM-1 occurred in areas with medullary or cortical differentiation of TETs and thymuses. B7 and LFA-3, absent in the normal cortex, were hyperexpressed in cortical type TETs. VCAM-1, confined to endothelium and dendritic cells in cortex and medulla, was focally expressed by epithelial cells of a medullary thymoma. We suggest that aberrantly expressed costimulatory molecules may contribute to the pathogenesis of paraneoplastic MG by an intratumorous activation of mature T cells.