Expression of Mum1/IRF4 in primary cutaneous large B-cell lymphoma. Neoplastic B cells of primary cutaneous large B-cell lymphoma of the leg show a positive staining for Mum1/IRF4 (A), whereas neoplastic cells of primary cutaneous follicle center cell lymphoma are Mum1/IRF4-negative (B) (original magnification × 200; Zeiss Axioshop 2 plus). Images were captured with a Leica DM6000B microscope (Leica, Rijswijk, The Netherlands), using an HCPlan APO objective lens (200×/0.70) and a ProgRes C10 camera with ProgRes10 software (JenaOptik, Jena, Germany).