Hematoxylin-eosin (H&E) stained SCCC tissue specimens. (A) Small, round tumor cells with a high nuclear/cytoplasmic ratio are arranged in solid sheets with a diffuse or trabecular pattern (magnification, ×40). (B) Adenocarcinomatous components are present in some of the cells and clusters of small cell carcinoma cells can be seen in the vessels (magnification, ×40). (C) Small cell carcinoma cells pervade, but do not infiltrate, beneath the squamous epithelium (magnification, ×100). (D) Immunohistochemical staining for neuron-specific enolase shows positive cytoplasmic staining of the tumor cells (magnification, ×100).