Abstract: Lesions of the skin or of a mucous membrane which is accompanied by formation of pus and necrosis of surrounding tissue, usually resulting from inflammation or ischemia. A break in skin or mucous membrane with loss of surface tissue, disintegration and necrosis of epithelial tissue and often pus. Ulceration occurs as a result of dermal or subcutaneous tissue loss, and it usually develops on the base of a tumoral or inflammatory nodule. Thus, an important part of the diseases in this chapter were also mentioned in other chapters of the book. Ulcerative lesions may sometimes develop due to trauma.