Beschreibung:
<jats:p><jats:bold>Background: </jats:bold> Lifetime risk for squamous cell carcinoma (SCC) of the skin is 1:30. Risk in organ‐transplant recipients (OTR) is increased over 60‐fold through long‐term drug‐induced immunosuppression. MAGE family‐derived peptides are cancer/testis antigens recognized by specific CD8<jats:sup>+</jats:sup> T cells and employed for immunotherapy. We were interested in the frequency and distribution of MAGE‐A4 in epithelial skin tumors of OTR and immunocompetent patients.</jats:p><jats:p><jats:bold>Methods: </jats:bold> mAb 57B predominantly recognizing MAGE‐A4 was used to stain 119 formalin‐fixed, paraffin‐embedded epithelial skin tumors (actinic keratosis, bowenoid actinic keratosis, Bowen’s disease, and SCC; n = 17, 25, 61, 16, respectively) in immunocompetent patients (n = 84) and OTR (n = 35).</jats:p><jats:p><jats:bold>Results: </jats:bold> All four epithelial skin tumors showed comparable immunoreactivity ranging from (25–71%, p = 0.361). Scattered immunoexpression pattern was more frequent in OTR (p = 0.025). SCC showed polarized immunoreactivity basally (p = 0.002).</jats:p><jats:p><jats:bold>Conclusion: </jats:bold> MAGE‐A4 was expressed in a large part of epithelial skin tumors with predominantly scattered immunoexpression pattern in OTR. The difference in immunoexpression pattern for immune status was limited, suggesting important non‐immunosuppressor‐mediated mechanisms for increased skin carcinogenesis in OTR. mAb 57B may be a helpful tool for immunohistochemistry and micrographic surgery using formalin‐fixed paraffin‐embedded tissue.</jats:p>