Case report 723

: An unusually large, noncalcified popliteal artery aneurysm causing cortical erosion was erroneously diagnosed as a soft-tissue sarcoma. The case stresses the importance of excluding a vascular cause of a mass whenever biopsy is considered. We review the clinical and radiological features of popliteal artery aneurysm and describe the appearance of the aneurysm on MR.