Perforin expression in eyelid sebaceous carcinomas: a useful and specific immunomarker for the differential diagnosis of eyelid carcinomas

PURPOSE: Eyelid sebaceous carcinoma (SC) remains a common diagnostic pitfall for both the clinician and histopathologist. The aim of this study was to describe perforin as a new marker in the immunohistochemistry panel for SC. METHODS: A total of 29 cases were retrieved from the Pathology archives, including 11 sebaceous neoplasms (nine SC; two sebaceomas), 10 squamous cell carcinomas (SCC) and eight basal cell carcinomas (BCC). These were stained using the monoclonal antibody for perforin, epithelial membrane antigen (EMA), Ber-EP4 and adipophilin (ADP). Sensitivity and specificity of perforin as an immunohistologic marker for sebaceous tumours were compared to EMA, ADP and Ber-EP4. RESULTS: Perforin stained strongly 9/11 (81%) of the sebaceous neoplasms (SN), 7/9 SC and 2/2 of sebaceomas (2/2), similar to ADP. Epithelial membrane antigen (EMA) stained 8/9 SC and was negative (1/2) or only very weakly expressed (1/2) in sebaceomas. The specificity of perforin in identifying SN versus SCC and BCC was 100% (95% CI 69-100), while EMA specificity in identifying SN varied according the comparison group (SCC: 50%, 95% CI 18-81, 100% (95% CI 63-100). Perforin better highlighted the intraepithelial spread of SC than EMA. Ber-EP4 was strongly expressed in six of nine SC, but was consistently negative in sebaceomas. CONCLUSIONS: The expression pattern of perforin in sebaceous neoplasms enables us to recommend the use of perforin as a new immunohistochemical marker for sebaceous neoplasms.