Subsequently, right lung biopsy was performed and pathological diagnosis was small cell carcinoma with immunohistochemistry: Pan-cytokeratin (PCK) (partial +), chromogranin A (CgA) (+), synaptophysin (Syn) (+), neural cell adhesion molecule-1 (NCAM-1/CD56) (+), thyriod transcription factor-1 (TTF-1) (+), cytokeratin-7 (CK7) (-), napsinA (-), Ki-67 (Li:70%). The gene discussed is KRT7; the disease is small cell carcinoma.