Diagnosis by CT images is increasing. But we often use X-ray images because of scanning time and scan cost. It is difficult to extract tumor region of X-ray images, and pathologists have to diagnose many images of tumor. Therefore, demand for the development of CAD system is increasing to support pathologists. Images that we use are dog images. Many people research human Images, but animal images are not researched well. In this paper, automatic extraction of tumor region is studied. We used operation of normalized correlation. Template of this filter looks like mountain. We also used Quoit-filter, that detected region that had possibility of tumor. We calculated edge of tumor to see easily tumors. Our method detected some tumor candidate edge. As future work, we should extract bone region, and some fixed value, including filter size should be automatically determined.