Cancer is still in the category of incurable diseases and is too much of a threat to people’s health. Once you have cancer, it is basically a death sentence! Just imagine how painful and helpless cancer patients are. But if it can be detected early, then the result is different, at least five years of survival rate can be guaranteed. We would not only wonder if there is any easiest way to detect cancer, but also to detect abnormalities at an early stage. The first thing that should come to our mind is whether or not we can detect abnormalities from routine blood tests. It is important to realize that routine blood tests are the most commonly used tests in hospitals, and they are also the ones that we often do in our daily tests. If doctors can detect abnormalities in the blood tests of cancer patients, then it should be very meaningful for early detection of cancer. Is this in fact the case? The actual situation is that a small number of cancer patients’ blood routine can be obviously abnormal, and the majority of cancer patients’ blood routine may be mildly abnormal or basically normal. The reasons for this are as follows: i. Generally, clinicians only notice changes in the number of cells of the three lineages (erythrocytes, leukocytes, and platelets) and hemoglobin, but the results of routine blood tests contain more information, such as information on the changes in the blood cells of malignant tumors that can be obtained from the results of the most common routine blood tests. Cancer can invade tissues all over the body, and red blood cells, white blood cells and platelets can all show corresponding abnormal changes during the development of cancer, and these abnormal changes can be seen through routine blood tests. Secondly, blood routine of hematologic cancer patients will indeed show obvious abnormalities, such as abnormal increase of white blood cells, abnormal decrease of white blood cells, red blood cells and platelets, etc. Doctors will further carry out bone puncture and other further examinations to make a clear diagnosis. Thirdly, in other cancer patients, the blood routine will not be as obviously abnormal as leukemia. However, since cancer is a chronic consumptive disease, some patients may have anemia in their blood routine, especially for middle-aged and old-aged patients. If anemia appears in the blood routine, the cause of the disease must be found out, especially if it is accompanied by long-term low fever and emaciation. Although not all cancers can be detected abnormally in routine blood tests, there are many ways to diagnose cancer through blood, such as tumor markers which are often used, and most cancers will have corresponding sensitive tumor markers. For example, CEA, CA199, CA72.4 are commonly used in gastric cancer; 2, tumor markers of colorectal cancer are similar to those of gastric cancer; 3, AFP of liver cancer; CA199 is relatively sensitive to pancreatic cancer; 4, PSA of prostate cancer; 5, markers of lung cancer are commonly used, such as SCC, NSE, CEA, CA125; 6, metastatic peritoneal carcinomas or primary peritoneal carcinomas often have the genetic value of CA125; 7, gynecological tumors, and so on. In addition, gynecological tumors often have CEA, CA125, CA153 and so on.