1. A method for contour-based determination of malignant tissue in a thermal image of a patient for cancer screening, the method comprising: receiving a thermal image of a patient for cancer screening, pixels in the thermal image with a higher temperature value being displayed in a first color and pixels with a lower temperature value being displayed in a second color, pixels with temperature values between the lower and higher temperature values being displayed in gradations of color between the first and second colors; analyzing the thermal image to identify a patch of pixels with an elevated temperature relative to a temperature of pixels associated with surrounding tissue; determining a boundary contour of the identified patch of pixels; calculating a measure of irregularity of the boundary contour; and determining, based on the measure of irregularity, that tissue associated with the pixel patch is malignant and non-malignant otherwise.