Blood tests cannot detect cancer cells. Cancer cells cannot be detected directly by blood tests only, and relevant tumor marker tests are needed. For example, carcinoembryonic antigen, glycan antigen 19-9, alpha-fetoprotein, squamous cell carcinoma antigen and so on.
Generally speaking, cancer cells cannot be detected through ordinary blood tests because the main values checked in ordinary blood tests are red blood cells, white blood cells, platelets and so on. If you want to check for cancer cells through blood tests, you can do so through blood tumor marker tests. The common ones are carcinoembryonic antigen, glycan antigen 19-9, alpha-fetoprotein, and squamous cell carcinoma antigen.
Patients who have high values after blood tumor marker tests may be retested or have another puncture test to clarify the cause and nature of the tumor.