DLL3 and small cell lung carcinoma: ASCL1, achaite‐scute homolog 1; CHGA, chromogranin A; CK, cytokeratin; CTC, circulating tumor cell; DAPI, 4′,6‐diamidino‐2‐phenylindole; DLL3, delta‐like ligand 3; EpCAM, epithelial cell adhesion molecule; IF, immunofluorescence; NEUROD1, neurogenic differentiation factor 1; OS, overall survival, PD‐L1, programmed cell death protein ligand‐1; PFS, progression free survival; POU2F3, POU class 2 homeobox 3; SCLC, small cell lung cancer; SLFN11, schlafen‐11; SYP, synaptophysin; Vim, vimentin; YAP1, Yes‐associated protein 1.