1. An image processing apparatus that analyzes a pathology image obtained by imaging an analysis object comprising: circuitry configured to: calculate an amount of a luminance difference characteristic as an amount of characteristic of each pixel of a pathology image, and set a cellular tissue region in the pathology image, based on the amount of the luminance difference characteristic, using a cellular tissue detector that has studied an image corresponding to a cellular tissue in advance, wherein the cellular tissue detector has studied the image in advance by statistical learning; determine the cellular tissue region to be a principal among a plurality of cellular tissue regions that exist in the pathology image based on at least a position of the cellular tissue region in the pathology image relative to a center of the pathology image; and calculate a principal degree score based on at least the position of the cellular tissue region, wherein the principal degree score increases as the position of the cellular tissue region is closer to the center of the pathology image.