In 2018 the Chicago Consensus Working Group for the first time developed guidelines for the treatment of appendiceal cancer; these endorsed the measurement of CEA, CA19-9, and CA125 in all patients with metastatic appendiceal cancer.34 However, in practice, even at this National Comprehensive Cancer Network–designated tertiary referral center, testing of all 3 tumor markers was not universal (eFigure 4 in Supplement 1). The gene discussed is MUC16; the disease is neoplasm.