Primary cutaneous extranodal natural killer/T-cell lymphoma misdiagnosed as peripheral T-cell lymphoma: the importance of EBV in situ hybridization for diagnosis

Cutaneous non-mycosis fungoides (MF) T- and NK/T-cell lymphomas are heterogeneous with different degrees of aggressiveness. Extranodal natural killer/T-cell lymphoma (ENKTL) is a predominantly extranodal lymphoma associated with EBV. In our recent Asian collaborative study on primary cutaneous ENKTL, we identified five patients initially misdiagnosed as various types of PTCL because EBER was not performed. Three patients were males and two were females, with a median age of 45 years (range 28~71 years). Based on the initial diagnoses (two as PTCL, two as primary cutaneous CD30-positive T-cell lymphoproliferative disorders and one as subcutaneous panniculitis-like T-cell lymphoma), all patients received CHOP chemotherapy and three with additional radiotherapy. All patients experienced persistent disease or relapse despite treatment (mean duration 11 months, range 1~24 months). These rare tumors often pose significant diagnostic challenges to the practicing dermatopathologists and (hemato)pathologists. We proposed to include EBER as a screening assay for primary cutaneous non-MF T-cell lymphoma, at least in East Asia where the relative frequency of such tumors is higher than in the West. As novel chemotherapy regimen SMILE (L-asparaginase, methotrexate, ifosphamide, etoposide, and dexamethasone) has been shown to be more effective than CHOP for ENKTL, a correct diagnosis of ENKTL is very important.