What is a lesion?


The word lesion is a general medical term used to describe any area of tissue that looks different from normal. A lesion can be caused by many things, including injury, infection, inflammation, or abnormal growth.

The term “lesion” does not explain what is causing the abnormality or whether it is harmful. It simply means that part of the tissue looks unusual.

What does “lesional” mean?

Lesional is an adjective that refers to something related to a lesion. For example, if a pathologist describes “lesional tissue,” they are referring to the area of tissue that shows the abnormality.

Does lesion mean cancer?

No. The word lesion does not mean cancer. Many lesions are noncancerous and can be caused by simple injuries, infections, or inflammation. Some lesions are precancerous, meaning they have the potential to turn into cancer over time. Only some lesions are cancerous tumors. Pathologists need to study the tissue carefully to determine what kind of lesion it is.

Why might the term lesion be used in a pathology report?

Pathologists sometimes use the word lesion when describing an abnormality before the exact cause is known. This may happen when the tissue looks different from normal but further tests are needed to decide whether it is due to infection, inflammation, a benign condition, or cancer. Using the word lesion communicates that something abnormal is present, even if the precise diagnosis is not yet clear.

Are all lesions tumors?

No. A tumor is a specific type of lesion made up of abnormal cell growth. Tumors can be benign (noncancerous) or malignant (cancerous).

However, many lesions are not tumors. Examples include:

  • Inflammatory lesions – Caused by infection or immune response, such as a swollen lymph node during a throat infection.

  • Traumatic lesions – Result from injury, such as a cut, bruise, or scar.

  • Degenerative lesions – Develop when tissue breaks down over time, such as in arthritis.

  • Precancerous lesions – Areas that show abnormal changes that may later turn into cancer, such as squamous intraepithelial lesions in the cervix.

So, while all tumors are lesions, not all lesions are tumors.

What are common examples of lesions?

Pathologists and other doctors encounter many types of lesions, depending on the body site.

Common examples include:

  • Skin lesions – Moles, rashes, or skin cancers such as melanoma.

  • Oral lesions – Sores or patches in the mouth, such as oral thrush or leukoplakia.

  • Liver lesions – Benign cysts or malignant tumors such as hepatocellular carcinoma.

  • Lung lesions – Abnormal spots seen on imaging that may represent infections, scars, or tumors such as lung cancer.

  • Bone lesions – Abnormalities such as fractures, cysts, or tumors like osteosarcoma.

  • Breast lesions – Benign changes such as fibrocystic tissue or malignant tumors like invasive ductal carcinoma.

How do pathologists evaluate a lesion?

To understand the cause of a lesion, pathologists examine tissue samples under the microscope. They may also use:

These tools help pathologists determine whether a lesion is due to infection, inflammation, a benign condition, or cancer.

Questions to ask your doctor

  • What type of lesion was found in my tissue?

  • Does this lesion look benign, precancerous, or cancerous?

  • Do I need a biopsy or other testing to better understand this lesion?

  • How will the presence of this lesion affect my treatment or follow-up?

  • Should I be monitored for changes in this lesion over time?

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