Interestingly, NKX2-1 (more commonly known as Thyroid Transcription Factor-1 or TTF-1), a common immunohistochemical marker of lung adenocarcinomas [39,40], was among the top 20 classification markers and had higher expression levels in lung SCC compared to HNSCC cancers. This evidence concerns the gene TTF1 and head and neck squamous cell carcinoma.