The ulcer as an morphological description for different diseases is heterogenous in histology. The tissue defect in the center of the ulcer appears in different forms; its base may either be covered with necrotic or fibrinous coatings, or it may show granulation tissue. Moreover, the ulcer edges strikingly show, necrosis, inflammation, or sgins of recovery. Indurations or underminings are characteristics of different ulcer types.
Source: Albertinen-Atlas