1. A method comprising: obtaining digital information describing a plurality of 2D x-ray tomosynthesis projection images of a patient's breast taken at different angles and at least one 2D x-ray projection mammogram image of the breast; using at least some of the information describing the tomosynthesis projection images to derive information describing 2D reconstructed tomosynthesis images representative of respective breast slices; wherein said reconstructed tomosynthesis images conform to a geometric coordinate system that matches a geometric coordinate system of the projection mammogram image such that anatomical structures that appear in the mammogram image appear at geometrically matching places in respective ones of the reconstructed tomosynthesis images; and displaying at least some of the mammogram image and the reconstructed tomosynthesis images.