Cancer cells cannot be directly observed through the naked eye, but only under the microscope. Cancer cells cannot be distinguished by naked eyes, only the excised tumor tissue can be seen by naked eyes, and the texture, color, morphology, and infiltration range of the tumor tissue can be generally observed, but further observation of the cancer cells needs to be carried out under the microscope. Pathological examination is usually required for the resected tumor tissue protrusion. Through a series of steps such as sampling, fixation, staining, sectioning, etc., thin slices of the resected tumor tissue are made, and then cancer cells and their characteristics can be searched for and observed under the microscope. A definitive diagnosis of cancer can only be made if the pathology examination finds cancer cells.