ulcer An open sore appearing on the skin or on a mucous membrane that results from the destruction of surface tissue. Ulcers may be shallow, or deep and crater-shaped, and they are usually inflamed and painful.
Skin ulcers most commonly occur on the leg (see leg ulcer), usually as the result of inadequate blood supply to, or drainage from, the limb. In some cases skin cancers, particularly basal cell carcinomas or squamous cell carcinomas, may be ulcerated. Rarely, a cancer may develop in the skin at the edge of a longstanding ulcer.
The most common types of ulcers of the mucous membranes are mouth ulcers, peptic ulcers, and those that occur in ulcerative colitis.
Ulcers may also affect the skin or mucous membranes of the genitalia
(see genital ulcer). Most genital ulcers are caused by sexually transmitted infections. Examples of this type of ulcer are hard chancres (see chancre, hard), which develop during the first stage of syphilis, and soft chancres (see chancroid). In addition, ulcers may develop on the cornea (see corneal ulcers).
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