Immunophenotypic Shift From CD8 to CD4 With Anaplastic Lymphoma Kinase (ALK)-Negative Anaplastic Large Cell Transformation in Mycosis Fungoides: A Case Report.

Mycosis fungoides (MF) classically presents with a CD4+/CD8- immunophenotype at the time of diagnosis. MF may extremely rarely present with CD8+/CD4- and, even more rarely, may shift between CD4+ and CD8+ phenotypes. To date, very few phenotypic shifts in MF have been reported, and just two of them were in the CD8+ to CD4+ direction. Our case report describes another instance of CD8+ to CD4+ phenotypic shift of MF, but with associated transformation to anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) - the first documented case of its kind. We hope to spread awareness about such rare phenomena to guide future research.