PET-CT examination does not detect all tumors in the whole body. PET-CT is a tumor positive test, which can reflect the information of tissue metabolism and lesion metabolism by using radiopharmaceuticals to participate in human tissue metabolism, and can detect tumors at an early stage. However, all tumors have their own specificity, some tumors have different enzyme composition, some tumors are better differentiated, in this case PET-CT examination is not advantageous, and multiple imaging combined with pathology is needed to confirm the diagnosis.