MUC16 and colorectal carcinoma: For possibility 1 to be true, elevations in serum tumor biomarkers would be more random than those observed in the clinic (elevated serum CA125 levels would be observed in liver metastasis, lung metastasis, bone metastasis, and other tumors, while elevated levels of serum cancer antigen 19–9 (CA19‐9) and cancer antigen 724 (CA724) are observed in CRC metastasis to the ovary).