(a) Percutaneous transthoracic needle biopsy specimen revealed monotonous, medium-sized cells infiltrating the lung tissue. Tumor cells have high nuclear cytoplasmic ratio and inconspicuous nucleoli (Hematoxylin & Eosin [H&E] staining, magnification, 200×). (b,c) Immunohistochemical stains revealed reactivity for cytoplasmic CD3, CD56 (magnification, 200×). (d) In situ hybridization for Epstein-Barr virus-encoded RNA (EBER) showed positive reaction in tumor cells (magnification, 200×).