A method for identifying biomarker-positive tumor cells is disclosed. The method includes, for example, reading a first digital image and a second digital image into memory, the first and second digital image depicting the same area of a first slide; identifying a plurality of nuclei and positional information of said nuclei by analyzing the light intensities in the first digital image; identifying cell membranes which comprise the biomarker by analyzing the light intensities in the second digital image and by analyzing the positional information of the identified nuclei; and identifying biomarker-positive tumor cells in said area, wherein a biomarker-positive tumor cell is a combination of one identified nucleus and one identified cell membrane that surrounds the identified nucleus.