A unique case of adolescent CD56-negative extranodal NK/T-cell lymphoma, nasal type.

Mature T-cell neoplasms are unusual in the pediatric population. The majority of these neoplasms in the United States are anaplastic large cell lymphomas (ALCL) characterized by CD30 and anaplastic lymphoma kinase-1 expression. Extranodal natural killer/T (NK/T)-cell lymphomas, nasal type, are extremely rare. Extranodal NK/T-cell lymphomas often express CD56, are associated with Epstein-Barr virus, and are negative for CD30. Clinically, extranodal NK/T-cell lymphomas are much more aggressive than ALCL, and require different treatment strategies. The authors present an adolescent male with a CD56 negative extranodal NK/T-cell lymphoma, nasal type. The lymphoma was partially positive for CD30, diffusely positive for EBV by in situ hybridization, and clonal for T-cell receptor gene rearrangement and cytogenetic abnormalities. The patient was aggressively treated with chemotherapy, surgery, and radiation. More than 2 years from completion of the therapy, the patient remains disease free. This case highlights the importance and difficulty of accurate identification of this type of rare tumor. We further present the literature review and discuss the diagnostic criteria for extranodal NK/T lymphoma using morphologic, immunologic, molecular, and cytogenetic information.