Primary central nervous system extranodal NK/T-cell lymphoma, nasal type with CD20 expression: Case report and review of the literature.

Primary central nervous system (PCNS) extranodal NK/T-cell lymphoma, nasal type (ENKTCL), is an exceedingly rare tumor. To the best of our knowledge, only 27 cases and only one reported aberrant CD20 expression have been documented in the literature. Here we present a second case of PCNS ENKTCL with aberrant CD20 expression in a 43-year-old immunocompetent Chinese female. The patient presented with tremors, weakness in the right upper limb, and a slow reaction. Magnetic resonance imaging revealed multiple brain lesions. A histological examination revealed a diffuse distribution of intermediate-sized pleomorphic lymphocytes with angiocentric growth. The tumor cells expressed CD2, CD3, CD56, T-cell intracellular antigen-1, granzyme B, and Epstein-Barr virus-encoded RNAs (EBERs), with additional partial and weak CD20 and CD30 expression. Despite a confirmatory pathological diagnosis, the patient refused treatment and was discharged, ultimately dying from the disease. In the literature review, the clinical, immunohistochemical, EBERs, treatment, and prognostic features of PCNS ENKTCL were summarized. Although PCNS ENKTCT is extremely rare, it does occur and should always be included in differential diagnoses. CD20 expression should be evaluated routinely with relevant markers. The accumulation of cases is crucial for developing an effective treatment strategy for this rare and aggressive malignancy.