The SOX2 gene encodes a member of the SRY-related HMG-box (SOX) family of transcription factors. SOX2 is expressed in multipotent neuronal stem cells, and may aid to identify cells that are capable of self-renewal and multipotent differentiation (1-3). SOX2 has been shown to be a negative prognostic factor and associated with aggressive phenotypes in breast, head and neck, gastric, colorectal and bladder cancers (4-10). In small cell lung cancers, SOX2 was also correlated with a poor prognosis. Conversely, SOX2 is expressed in a high percentage of lung squamous cell carcinomas and was shown to be an independent positive prognostic marker (11-14).