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MyPathologyReport Printed: October 30, 2026

Ulcer: Definition

An ulcer is an injury in which the surface cells of a tissue are lost. The loss exposes the tissue underneath. Ulcers most often occur on the skin, in the stomach, and in the mouth. They can occur almost anywhere in the body.

An ulcer is a finding, not a diagnosis. It describes what the pathologist saw under the microscope. The cause of the ulcer is a separate question. This article explains what an ulcer is, how it differs from an erosion, what causes ulcers, and what the wording on your report means.

What is an ulcer?

An ulcer is a break in the lining of a tissue. The lining of most organs is a layer of cells called the epithelium. In an ulcer, the epithelium is completely gone in one area. The connective tissue underneath is exposed to the surface. The open area often looks like a crater.

How is an ulcer different from an erosion?

An ulcer is deeper than an erosion. An erosion removes only the epithelium. It does not reach the submucosa or the tissue under the skin. Erosions usually heal with little or no scarring. An ulcer goes deeper, so it heals more slowly and can leave a scar.

Where do ulcers occur?

Ulcers can form wherever a surface lining exists. The most common sites are:

What causes an ulcer?

Any process that damages surface cells and slows healing can cause an ulcer. Common causes include:

What does an ulcer look like under the microscope?

Under the microscope, an ulcer shows a complete loss of the surface epithelium. Older ulcers often show several layers:

The tissue next to the ulcer often shows inflammation too. In the stomach, doctors call this gastritis. Granulation tissue also signals healing. It appears as the ulcer begins to mend.

How is an ulcer identified?

A pathologist identifies an ulcer by examining a biopsy under a microscope. The pathologist looks for the missing surface lining and the changes in the tissue below. The pathologist also looks for a cause. In the stomach, for example, the pathologist looks for H. pylori. The pathologist also checks the sample for tumor cells because some cancers form ulcers.

What might my report say about an ulcer?

Reports describe an ulcer in a few standard ways. Each laboratory phrases it a little differently:

Is an ulcer cancer?

An ulcer is not cancer. It is a loss of surface lining. However, some cancers form an ulcer as they grow. For this reason, doctors and pathologists check ulcers for tumor cells. Your report will state whether the pathologist found tumor cells.

What happens after an ulcer is identified?

Next steps depend on the cause and location. Doctors treat the cause so the ulcer can heal. Some ulcers bleed, so your doctor may ask you to watch for signs of bleeding. Your doctor may repeat the biopsy to check that the ulcer has healed. Your doctor can explain the plan for your ulcer.

Questions to ask your doctor

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