1. A computer implemented image processing method of identifying a tissue boundary of a tumour region of a tissue sample, the tissue sample containing non-tumour regions and at least one tumour region, to enable excision of at least a portion of a tumour region from the tissue sample by cutting along the tissue boundary, the method comprising: obtaining an image of a tissue section of the tissue sample; identifying at least one image property of the image; comparing the image property with classification data; based on the comparison, classifying a region of the image as a tumour region representing a tumour region in the tissue sample or a non-tumour region representing a non-tumour region in the tissue sample; and if the region of the image is classified as a tumour region, identifying a boundary of the region of the image; and using the boundary to identify a tissue boundary of the tumour region of the tissue sample represented by the region of the image.