Reactive changes

The Pathology Dictionary Team
February 24, 2023

What are reactive changes?

In pathology, the term ‘reactive changes’ is used to describe cells or tissues that look abnormal as a result of changes in their environment. These changes can include infection, physical injury, medication, and inflammation. Reactive changes are benign (non-cancerous).

What causes reactive changes?

Anything that changes the environment of a tissue can cause the cells in the tissue to show reactive changes. For example, common causes include inflammation, viral or bacterial infections, medications/drugs, physical trauma/stress on a tissue, and radiation. Reactive changes can also be seen in the non-cancerous cells surrounding a benign (non-cancerous) or malignant (cancerous) tumour.

What does it mean if my pathology report says ‘favour’ reactive?

Pathologists use the term ‘favour’ when the features seen under a microscope are most likely reactive but when other types of changes cannot be completely excluded. For example, sometimes it can be difficult for a pathologist to tell the difference between reactive changes and a type of abnormal growth called ‘dysplasia’. This is because both of these two conditions share many microscopic features. In this situation, ‘favour’ would be used to show that there was some uncertainty with the diagnosis and that further diagnostic tests may be necessary.