DLL3 and small cell lung carcinoma: Delta‐like ligand 3 (DLL3) is an atypical ligand for NOTCH receptors that is expressed on SCLC stem cells (Saunders et al, 2015), circulating tumor cells (Messaritakis et al, 2019; Obermayr et al, 2019), and metastases (Sharma et al, 2017).