Fli-1 expression in mycosis fungoides

Background: The Fli-1 transcription factor functions in cellular proliferation and tumorigenesis. Its role in various neoplasms and its presence in lymphocytes suggest a link between Fli-1 dysregulation and the pathogenesis of mycosis fungoides (MF). In this study, we further elucidate this possible link. Methods: Sections from archived specimens were stained using a polyclonal antibody against Fli-1. The percentage of nuclei showing Fli-1 expression was recorded. These were compared with reactive dermatoses. Results: All of the tumor stage lesions showed high levels of nuclear Fli-1 expression. Of plaque stage lesions, six of 12 (50%) showed the same intensity, while the remaining six of 12 varied significantly in their Fli-1 expression. The few patch stage lesions also showed varied expression. Conclusion: This study shows diffuse nuclear expression of Fli-1 in all tumor stage MF, whereas expression of this transcription factor varied widely in the early, epidermotropic stages. Although the numbers are too small to draw statistical significance, this study demonstrates an association between increased expression of Fli-1 and progression to tumor stage MF that merits further investigation. Additionally, the mixed expression of Fli-1 in the epidermotropic stages suggests that the role of Fli-1 in MF is related to neoplasia and not epidermotropism.