Primary spinal extranodal NK/T‐cell lymphoma diagnosed by fine‐needle aspiration and core biopsy

We report an extremely rare case of primary spinal extranodal NK/T‐cell lymphoma (PSENKTL). A 54‐year‐old man presented with fever of unknown etiology for 2 months, with clinical evidence of hemophagocytic lymphohistiocytosis. Imaging studies revealed multiple spinal lesions without evidence of disease in other body sites. Fine‐needle aspiration and core biopsy (FNACB) of a paraspinal mass showed a monotonous population of intermediate lymphocytes with abundant cytoplasm with fine granules, round to slightly irregular nuclei, and inconspicuous nucleoli. Core biopsy revealed diffuse infiltration by cells with a NK cell phenotype, positive Epstein–Barr virus‐encoded small RNA, and negative T‐cell receptor gene rearrangement. Bone marrow biopsy showed the presence of hemophagocytosis without evidence of lymphoma. The disease disseminated to the small bowel late in the clinical course and the patient died shortly after admission. This unusual case was diagnosed by FNACB and raised awareness of ENKTL as a differential diagnosis in spinal lesions.