Which of the following is a characteristic of an ulcer?

An ulcer is characterized by the presence of an open sore, which results from the breakdown of tissue. This process typically occurs in cases where there is a loss of the protective layer of skin or mucous membrane, leading to exposure of underlying tissue. This open sore can be painful and may have associated symptoms like inflammation or infection, depending on its location and underlying cause.

In contrast to this, a raised lesion suggests a different pathology, often associated with growths or tumors, which does not accurately describe ulcers. Similarly, benign growths refer to non-cancerous masses that do not necessarily involve tissue breakdown or sores. Lastly, a flat discoloration of the skin indicates a superficial alteration in color without tissue loss or damage, which is also not characteristic of ulcers. Overall, the defining feature of an ulcer is indeed the presence of an open sore resulting from tissue destruction.