Low-level DLL3 mRNA expression has been detected in pituitary, brain, and testis (9) but, importantly, not on the cell surface of nonmalignant cells (8), making it an attractive tumor-specific target for antibody-drug conjugates (8, 10), bispecific T cell engagers (11, 12), and CAR T cells. The gene discussed is DLL3; the disease is neoplasm.