Wrong question. Cancer cells are identified visually by other abnormal features of the cells related to their nucleus, vacuoles, and granules and how those features different from normal cells and how many and where the cells are. The nature of the cells is further clarified by flow cytometry which identifies surface protein markers of the cells the pattern of which can tell you if the cell is abnormal or immature. Leukemias are often first identified by the presence of immature white cells in the peripheral blood or an abnormal quantity of certain types of white cells. All immune cells in your blood appear white when separated from rbcs, but when looked at under the microscope they are stained and appear with dark blue nucleuses and blue to pink or red cytoplasm.