Do all cancers show on bloodwork..?

No unfortunately: In fact, most do not.

That'd make it easy.: It's quite the opposite. Blood work rarely helps diagnose cancers with a few exceptions: leukemias. A sudden increase in psa levels could indicate prostate ca. Abnormal liver chemistries usually mean other problems, but metastatic disease to liver may cause it. High calcium could mean cancer in the bone, but this is not usually the cause. Most cancers can not be picked up with bloodwork.