This 46-year-old female had a long history of Crohn disease. She began developing subcutaneous nodules on her upper extremities. Involvement of the skin is often called "metastatic Crohn disease", as lesions disseminate to distant sites away from the GI tract. The histology in this case is typical, showing noncaseating granulomas. The histologic differential diagnosis would include sarcoidosis and infectious processes.
The infiltrate consists of histiocytes, aggregating into well-formed granulomas. The granulomas are noncaseating with a peripheral rim of lymphocytes. Multinucleated Langhans-type giant cells are present. Polarizable foreign material was not found. Special stains for microorganisms were negative (not shown).