How long can a cancer cell survive in a drop of blood spilled on a counter. i assume not long but are we talking minutes, an hour, many hours? thx

Not relevant: A tumor cell in a drop of blood is not infectious and it does not matter how long it is alive. Just observe universal precautions while dealing with body fluids including, blood. Most cancer cells in blood are irrelevant to any disease.

Not catching: Cancer cells are very fragile and will die as soon as the drying process begins. You cannot catch a malignancy from another person; your body will reject the cell as it would a transplant. If this were not the case, then people who get blood transfusion -- and a fair number of donors must have unknown cancers cells in their blood -- would come down with metastatic disease. It doesn't happen.