Abstract: A computer implemented method is provided for determining an amount of tumor cells in a tissue sample. The method includes obtaining first image data describing an image of a tissue sample at a first resolution, obtaining second image data describing the image at a second resolution, wherein the first resolution is lower than the second resolution, selecting a candidate tumor region from the second image data based on texture data determined from the first image data, identifying a tumor structure in the candidate region of the second image data, and determining a number of cells in the tumor structure based on its area and an estimate of tumor cell area to estimate an amount of tumor cells in the tissue sample.