An Unusual Case of EBV-Negative Primary CNS Lymphoma of Natural Killer/T-Cell Lineage.

Extranodal NK/T-cell lymphoma (ENKTL) is a well-defined cytotoxic lymphoma strongly associated with Epstein-Barr virus (EBV) infection, commonly affecting the nasopharynx and upper aerodigestive tract. Primary central nervous system (CNS) involvement is rare, and only 17 cases were previously reported in the literature. Here, we report the case of a 44-year-old male admitted with a 3-month history of personality changes and progressive right leg weakness. Brain magnetic resonance imaging studies (MRIs) revealed multiple rim-enhancing brain lesions bilaterally. An extensive clinical and laboratory workup was unrevealing, and 2 brain biopsies were initially considered inconclusive. Pertinently, no systemic lymphoproliferative disorder was identified. The patient initially experienced remarkable clinical improvement with dexamethasone, pulse methylprednisolone, and rituximab therapy. However, he eventually had rapid clinical deterioration, was found to have increased brain lesions, and died nearly 6 months after the initial presentation. During this time, the second brain biopsy was found to show involvement by T-cell lymphoma of NK-cell lineage, which was EBV negative. No post-mortem examination was done to identify any systemic lymphoma. This case serves to expand the spectrum of lymphomas involving the CNS.