The clinical features of the so-called leukemia-like reaction are mainly the abnormally high number of white blood cells in the peripheral blood picture. In severe bacterial infections, leukocytes can be abnormally high, but rarely exceed 30,000 or more. However, leukemia is mainly an abnormal proliferation of leukocytes in the bone marrow, whether it is lymphocytic or granulocytic leukemia, due to the proliferation of abnormal cells, which can reach more than 100,000 or hundreds of thousands of leukocytes in the peripheral blood picture. The presence of a large number of naive cells can be the differential diagnosis. The abnormal proliferation of naive granulocytes and leukocytes in the bone marrow results in the suppression of red blood cells and platelets, which can lead to clinical anemia and bleeding due to thrombocytopenia. The whole body reticuloendothelial system, liver, spleen, and lymph nodes seem to be invaded, and the progression is particularly rapid clinically. If this condition is suspected, it is finally possible to make a definitive diagnosis. The leukemia-like reaction does not have these characteristics, except for infection control, and the blood picture sometimes shows obvious signs of improvement, so this can be differentiated.