The interface reaction pattern in the skin: an integrated review of clinical and pathological features

Not uncommonly, pathologists encounter biopsies displaying inflammation at the dermoepidermal junction and confronted with its numerous diagnostic possibilities. As with other inflammatory dermatoses, the correct diagnosis relies on careful integration of clinical, laboratory, and histopathological features. Knowledge of clinical aspects of these disorders is crucial, and at times, lack of training in clinical dermatology can make clinicopathological correlation challenging for the pathologist. This review is organized following the classical classification of cell-poor (vacuolar) and cell-rich (lichenoid) interface processes. The various entities are described based on their clinical presentation along their clinical differential diagnosis followed by their histopathological features and pathological differential diagnosis. Our aim is to provide an updated, clinically relevant review that integrates nuanced clinical and pathological features, with an emphasis on clues that may help differentiate entities in the differential diagnosis.