Fig. 3

a Operative specimen revealing a lung tumor measuring 40 × 30 mm. b Histopathological examination with hematoxylin and eosin staining of the tumor showed an undifferentiated carcinoma with poorly defined nests of neoplastic cells and a stroma exhibiting prominent lymphoplasmacytic infiltration (× 200). c, d Positive staining for CD3 (c; × 400) and CD8 (d; × 200) in lymphocytes around the tumor. e Positive staining for latent membrane protein 1 (× 400)