This is a section of the cat's gut. You can see serosa, muscularis, submucosa, mucosa, and tumor on this slide. The tumor has arisen from the submucosa and has infiltrated toward the lumen of the bowel where is has ulcerated the mucosa. It is a space-occupying lesion and is partially occluding the lumen of the bowel. Hemorrhage and debris can be seen within the lumen near the ulcerative lesion. You can see from here that the tumor is markedly basophilic and focally disseminated. This suggestes that it is highly cellular and is locally aggressive.