CEACAM5 and neuroendocrine carcinoma: CEA: carcinoembryonic antigen; CYFRA: cytokeratin antigen; SCLC: small-cell lung cancer; LCNEC: large-cell neuroendocrine carcinoma; HGNEC-P: POU2F3-dominant high-grade neuroendocrine carcinoma; HGNEC-non-P: non-POU2F3-dominant high-grade neuroendocrine carcinoma