New entities in dermatopathology

This article discusses some recently described entities in dermatopathology that are uncommon but important to recognize. The interstitial granulomatous drug reaction was described in 1998 and shares some differential diagnoses with palisaded neutrophilic and granulomatous dermatitis, an entity that has been given many different names. Nephrogenic fibrosing dermatopathy and calciphylaxis are rare but important conditions occurring in patients with renal failure. The seriousness of a diagnosis of calciphylaxis and of cholesterol embolization syndrome must be communicated to clinicans as a matter of urgency. Cutaneous Rosai Dorfman disease and acute generalized pustulosis are important in that their prognosis is excellent and good news for the patient. Superficial pyoderma gangrenosum and granuloma faciale are included as not-so-new entities whose features are not commonly known and which may be underdiagnosed.