CEACAM5 and non-small cell squamous lung carcinoma: Carcinoembryonic antigen (CEA)-related cell adhesion molecule 5 (CEACAM5, also known as CD66e), a cell surface glycoprotein, is reportedly upregulated in several tumor types, including non-squamous non-small-cell lung cancer, and plays a key role in tumor progression by inhibiting apoptosis, blocking cell differentiation, and regulating metastasis [1, 2].