Dermatologists recognize most skin diseases based on their appearance, location on the body and behavior over time. Occasionally, these criteria are not enough and a skin biopsy is taken to be examined under the microscope.

This microscopic examination, called Dermatopathology, reveals the identity of the disease and clarifies the diagnosis. Occasionally, additional testing needs to be performed on skin samples, such as immunofluorescence, electron microscopy or flow cytometry.