CD30-Negative Cutaneous T-Cell Lymphomas Other than Mycosis Fungoides

Cutaneous T-cell lymphomas (CTCLs), other than mycosis fungoides/Sézary syndrome and the group of cutaneous CD30+ lymphoproliferative disorders, are rare. These include subcutaneous panniculitis–like T-cell lymphoma (SPTCL); extranodal natural killer/T-cell lymphoma, nasal type; primary cutaneous peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS); and rare subtypes of PTCL, NOS. Apart from SPTCL and primary cutaneous CD4-positive small-medium pleomorphic T-cell lymphoma, these lymphomas have in common aggressive clinical behavior and poor prognosis. Differentiation between these different types of CTCL may be difficult and requires integration of histopathologic findings with clinical data and the results of phenotypic and often molecular genetic studies.