CD123 staining in patients with ECD. ECD anti–CD123 immunostaining is negative in 5 cases (patients no. 6, 7, 9, 14, and 15); in 1 case (patient no. 4) rare cells are positive for CD123 (filled arrowheads). Samples were obtained from blocks containing infiltrated pericardium (patient no. 4), perirenal fat (patients no. 6, 7, and 9), peritoneum (patient no. 14), and aorta (patient no. 15). A cutaneous blastic pDC tumor sample was used as positive control (immunoperoxidase method, magnification ×200).