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What is the Cause of This Cystic Nodule on the Knee?

What is the Cause of This Cystic Nodule on the Knee?

This education series for dermatologists is presented by the Weill Cornell Comprehensive Dermatopathology Service.  

figure 1 and 2

Case: A 58-year-old man with a history of myelofibrosis presented with a cystic nodule on his left knee. The papulocystic lesion had been present for 2 months and would periodically drain, although there would invariably be a recollection of fluid. He had had a stem cell transplant previously. Also of interest, in November 2018, he was diagnosed with fusarium and had received 6 weeks of amphotericin. A biopsy was performed. 

What is the best diagnosis? 

A. Phaeohyphomycosis
B. Protothecosis 
C. Limited cutaneous Wegener granulomatosis
D. Superficial granulomataous pyoderma gangrenosum
E. Kerion celsi

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