A pathological section is a type of tissue section, and a section made of diseased tissue is called a pathological section. All living things in the world are made up of cells, and so is a human being. A human being’s illness is essentially a lesion in the cells that make up diseased tissues or organs, and if changes in the cells can be observed, it is possible to determine the disease morphologically and thus make a pathological diagnosis. Sometimes it is difficult for doctors to confirm the diagnosis from the clinical signs and symptoms of patients alone, and even through ancillary examinations, such as imaging and biochemical examinations, it is still difficult to determine the disease, and then pathological diagnosis may be needed to make the final diagnosis. Especially for tumor diseases, firstly, the clinician removes the lesion tissue through surgery and sends it to the pathology department, then the pathologist observes it, cuts the lesion into 3-4μm thick slices and attaches the slices to the slides, such slices with pathological tissue are pathological sections. After the pathological section is made and then put on the microscope for observation, the type of disease can be judged from the cellular changes observed on the microscope, and this is the significance of making pathological section.