Interface changes

The phrase interface changes is used by pathologists to describe a specific pattern of inflammation and damage seen at the junction between the epithelium (the surface layer of cells that lines the skin, mouth, and other mucosal surfaces) and the underlying connective tissue (called the dermis in skin or lamina propria in mucosal tissue). This area is known as the epithelial-connective tissue interface.

A key feature of interface change is damage to the basal cell layer, which is the bottom row of cells in the epithelium. Basal cells are responsible for renewing and repairing the surface layer of tissue. In interface change, these basal cells are often the main target of the immune system, and they may appear shrunken, dark, or fragmented under the microscope. These signs indicate that the cells are undergoing stress or cell death (a process called apoptosis).

Where are interface changes seen?

Interface changes are most commonly seen in tissue from areas lined by squamous epithelium, such as:

• Skin – where the finding is often called interface dermatitis.

• Mouth and oral cavity.

• Esophagus.

• Genital and anal mucosa.

They are often described in biopsy reports when a sample is taken to investigate symptoms like a rash, ulcer, or chronic inflammation.

What causes interface changes?

Interface changes can be caused by a variety of conditions, most of which involve the immune system reacting against the basal cells of the epithelium.

Common causes include:

• Autoimmune and inflammatory diseases, such as lichen planus, lupus erythematosus, graft-versus-host disease (GVHD), and erythema multiforme.

• Viral infections, especially herpes simplex virus (HSV) and HIV.

• Drug reactions, where the immune system attacks the skin or mucosa in response to a medication.

In each case, the basal cells are damaged, leading to the pattern known as interface change.

What do interface changes look like under the microscope?

When viewed under the microscope, interface change shows:

• Injury to the basal cell layer, with cells appearing shrunken, dark (hyperchromatic), or dying.

• Lymphocytes, a type of immune cell, collecting along the epithelial-connective tissue interface.

• Separation or disruption at the junction between the epithelium and the underlying tissue.

• In more severe cases, blistering may occur as the connection between the layers is weakened.

This pattern reflects a focused immune response directed at the basal cells, disrupting the normal renewal and stability of the epithelium.

Is interface change a diagnosis?

No. Interface change is not a diagnosis on its own. It is a microscopic pattern that pathologists describe when they see signs of basal cell damage and immune activity at the epithelial interface. It can be seen in many different conditions, so the final diagnosis depends on:

• The overall pattern of inflammation and other changes.

• The location of the tissue sample.

• Your medical history and symptoms.

• Results of other tests, such as immunofluorescence or blood work.

Your doctor will combine this information with your pathology report to determine the cause and whether any treatment or follow-up is needed.

Questions to ask your doctor

• What condition is causing the interface changes in my tissue?

• Are the basal cells in the sample significantly damaged?

• Do I need more tests to confirm the diagnosis?

• How will these findings affect my treatment plan?

• Is this condition chronic or likely to resolve on its own?