TTF1 and squamous cell carcinoma: Current reports have shown that poorly differentiated NSCLC with TTF-1/p40 co-expression is associated with factors including male sex, older age, smoking history, poor histological differentiation, dual immunohistochemical features of adenocarcinoma and squamous cell carcinoma, lack of typical genetic changes in adenocarcinoma or squamous cell carcinoma, rapid clinical progression, and poor prognosis.