Clues in Histopathological Diagnosis of Panniculitis

Background: Panniculitides comprise a group of heterogeneous inflammatory diseases. Nevertheless, histopathological study along with clinicopathological correlation usually led to a specific diagnosis. In most textbooks, the first step in the diagnosis is to classify them as mostly septal or lobular depending on where the inflammatory infiltrate is located. The second step is deciding if vasculitis is present or not. Finally, the third step is further characterizing the inflammatory infiltrate. However, in addition to the algorithmic approach to panniculitis diagnosis, some subtle changes may help to the diagnosis. Objective: To review some clues in panniculitis dermatopathological diagnosis such as presence of granulation tissue, sclerotic connective tissue septa, small granulomas arranged around a central clear space, so-called ghost adipocytes, needle-shaped crystals, small lobules with a proliferation of capillaries, Splendore-Hoeppli phenomenon, refractile microspheres, neutrophilic infiltrates, granulomas and fibroplasia or presence of adipose tissue in dermis. Methods: We have compiled 12 clues based in our personal experience in this field. Limitations: Specificity and sensibility of every clue may vary and these clues are a guide to correct diagnoses that should rely in clinicopathological correlation. Conclusion: Knowledge of these 12 clues will help to increase the diagnostic accuracy in panniculitis diagnosis.