Primary cutaneous γδ T-Cell lymphoma positive for both T-Cell Receptor γ and T-Cell Receptor β

Primary cutaneous γδ T-cell lymphomas (γδ CTCLs) was first described in 1991, and in 2008, it was classified as a provisional form of cutaneous T-cell lymphoma by the World Health Organization. This is considered a highly aggressive lymphoma, and because of the rarity and lack of clearly defined diagnostic features, it can represent a considerable diagnostic challenge. Diagnosis of γδ CTCL requires demonstration of the γδ T-cell receptor (TCR) and absence of the αβ TCR. Until recently, no reliable antibody for formalin-fixed paraffin-embedded sections against the γδ TCR existed, and most γδ CTCLs were diagnosed in absence of the TCR-β and presence of a compatible cytotoxic immunophenotype (CD4/CD8, granzyme). However, because some lymphomas are TCR silent and thus not belonging to the γδ-lineage, this approach should not stand alone. We present a case of γδ CTCL that illustrates the difficulties in diagnosing this type of lymphoma both histopathologically and clinically. This case was particularly challenging because the neoplastic T cells displayed immunohistochemical positivity for both TCR-γ and TCR-β. Therefore, TCR-β may be aberrantly expressed in γδ CTCL, and positive staining for TCR-β alone cannot be used to exclude the diagnosis of γδ CTCL.