KRT7 and squamous cell carcinoma: Lung adenocarcinomas express cytokeratin 7 (CK7) and in most cases thyroid transcription factor-1 (TTF-1), where the latter is considered lineage-specific as it is essentially not expressed in squamous cell carcinoma (Vidarsdottir et al. 2018; Kadota et al. 2015; Kriegsmann et al. 2019; Roberts et al. 2020).