In the context of lung adenocarcinoma scRNA-seq analyses, Kim et al. annotated canonical markers such as PECAM1, CLDN5, Fms-like Tyrosine Kinase 1 (FLT1), and Receptor Activity Modifying Protein 2 (RAMP2) to delineate PEC lineages (Kim et al., 2020). Here, FLT1 is linked to lung adenocarcinoma.