Metastatic Crohn's disease: a histopathologic study of 12 cases.

Perhaps, the most intriguing cutaneous sequela of Crohn's disease (CD) is 'metastatic' CD, defined as sterile granulomatous skin lesions arising at sites discontinuous from the gastrointestinal tract. Though various histopathologic patterns have been described, a lack of a large series has precluded a comprehensive characterization and distinction from the pathologic differential diagnoses. The histopathology features of 12 new cases of metastatic CD were reviewed. Non-suppurative granulomata with a slight cuff of lymphocytes in a nodular or diffuse pattern with an associated superficial and deep perivascular mixed inflammatory infiltrate was the most common pattern. Other common features included an accompanying infiltrate which was often rich in eosinophils, and ulceration of the overlying epidermis. These features are emphasized as potentially useful in distinguishing this entity from its greatest mimicker, cutaneous sarcoidosis.