Primary Cutaneous T-Cell Lymphoma Positive for Both T-Cell Receptor and T-Cell Receptor

Primary cutaneous T-cell lymphomas ( 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 CTCL requires demonstration of the T-cell receptor (TCR) and absence of the TCR. Until recently, no reliable antibody for formalin-fixed paraffin-embedded sections against the TCR existed, and most CTCLs were diagnosed in absence of the TCR- and presence of a compatible cytotoxic immunophenotype (CD4−CD8−, granzyme). However, because some lymphomas are TCR silent and thus not belonging to the -lineage, this approach should not stand alone. We present a case of 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- and TCR-. Therefore, TCR- may be aberrantly expressed in CTCL, and positive staining for TCR- alone cannot be used to exclude the diagnosis of CTCL.