Primary pulmonary presentation extranodal NK/T-cell lymphoma, small cell variant, illustrating the value of flow EBER in situ hybridisation assay.

A 57-year-old male from Guinea presented with 6 months of progressive shortness of breath, productive cough, and occasional night sweats. A lung biopsy revealed an angiocentric pulmonary infiltrate of small bland lymphocytes and lymphoepithelial lesions mimicking a MALT lymphoma. The infiltrate expressed CD3, CD56, and Epstein-Barr virus-encoded RNA with little Ki-67 staining. Blood EBV copies were 519 IU/mL. FDG-PET scan showed no uptake outside the thorax. A diagnosis of small-cell variant pulmonary NK/T-cell lymphoma was made. Following asparaginase/cisplatin-based treatment, the patient developed recurrent cough, and nasal biopsy suggested lymphoma relapse. Following transplant conditioning, the patient developed symptoms of fever and cough, with rising blood EBV load. Lymphoma progression was suspected. A flow RNA assay demonstrated a small population of EBER + CD8 + T-cells in blood. NK/T-cell lymphoma usually present with sino-nasal symptoms. The small-cell variant is rare. The diagnosis is challenging when the clinical presentation and cytological features are atypical. POT1 variants have not been reported in ENKTL to our knowledge, but germline variants have been associated with lymphomas. A multicolour EBER hybridisation flow assay can help identify the cellular origin of EBV reactivation.