1. An apparatus configured to generate a report based on diagnosis target images, comprising: a derivation unit configured to derive image characteristic conditions to identify a plurality of diagnosis target images specified by a user as a group; a determination unit configured to determine search conditions of images similar to the diagnosis target images by using the image characteristic conditions derived by the derivation unit; a search unit configured to search a database for one or more similar images satisfying the search conditions; and an extraction unit configured to extract image findings satisfying predetermined conditions from image findings attached to the one or more similar images obtained by the search unit.