Pagetoid reticulosis tumor cells with double expression of TCRγδ and TCRαβ: an off-target phenomenon or genuine expression?

Pagetoid reticulosis (PR) is a low-grade primary cutaneous T-cell lymphoma showing localized patches or plaques with an intrapeidermal proliferation of neoplastic T-cells with heterogeneous immunophenotype. We describe a 73-year-old woman with a 8-year history of gluteal lesions of PR, whom large blast cells were CD4/CD8 double negative T-cells with an activated cytotoxic profile. The case was investigated using a broad panel of monoclonal antibodies including TCRγM1, a new available antibody that recognizes the γ chain subunit of the T-cell receptor (TCR) in formalin-fixed paraffin-embedded tissue. Large blast cells were simultaneously positive for TCRαβ and TCRγδ with an activated cytotoxic phenotype. It is worldwide accepted the mutual exclusive expression of TCRαβ and TCRγδ but six different studies, dealing with TCRγδ expression in various types of extra-nodal lymphomas, reported cases whom tumor cells expressed simultaneously TCRαβ and TCRγδ. Our data and those of similar reports, suggest the possibility of existence of a subset of extra-nodal T-cell lymphomas showing simultaneous expression by tumor cells of TCRγδ and TCRαβ with an immunoprofile consistent with an origin from TCRγδ+ T lymphocytes. This unusual subset has preferential, but not exclusive, skin localization and variable epidermotropism.