Introduction Vascular injuries complicating frac- tures of the humerus are uncommon [1, 2, 3, 4, 5]. Two cases of pseudo- aneurysm formation following closed fractures of the proximal hu- merus are presented. The imaging features are illustrated, including the characteristic appearances at mag- netic resonance imaging (MRI). Both cases presented for investiga- tion of a mass, suspicious for malig- nancy, which developed 6 and 18 months, respectively, after the original injury. Diagnosis was de- layed in both cases due to the ab- sence of pulsatility of the mass and the presence of peripheral perfusion. MRI provided the definitive diagno- sis, displaying tissue characteristics of altered blood and flow artifact. The possibility of vascular injury should be considered when analyz- ing images of a soft tissue mass of the extremity in the context of previ- ous trauma. Case reports Case 1 A 60-year-old woman presented with painful swelling of her left upper arm, resulting in progressive loss of function. The swelling had devel- oped gradually over the 6 months prior to presentation. She had sus- tained a closed fracture of the left proximal humerus, due to a fall downstairs, immediately prior to the development of the progressive up- per arm swelling (Fig. 1A). The frac- ture was treated conservatively but the patient was subsequently lost to follow-up for several months. There was a history of alcohol abuse but past medical history was otherwise unremarkable. Examination revealed a localized mass in the left upper arm. No pulsa- tions were palpable in the mass. The radial and brachial pulses were nor- mal. There was no neurological defi- cit but the range of movement of the arm was markedly restricted. Laboratory tests results revealed a mild anemia with hemoglobin levels of 10 g/dl. Platelet levels and coagu- lation profile were normal. Radiographs of the left humerus showed marked resorption and dis- tortion of bone adjacent to the site of the previous fracture. There was a large surrounding soft tissue mass Received: 5 October 2000 Revision accepted: 3 July 2001 Published online: 19 September 2001 © ISS 2001 C.J. Roche ( ✉ ) · W.C. Torreggiani P.L. Munk Department of Radiology, Vancouver General Hospital, 855 West 12th Ave, Vancouver, V5Z 1M9, Canada e-mail: clareroche@hotmail.com Tel.: +1-604-8754340 Fax: +1-604-8754806 D.A. Ritchie · R. McWilliams Department of Radiology, Royal Liverpool University Hospital, Liverpool, UK M. Jane Department of Orthopaedic Surgery, Royal Liverpool University Hospital, Liverpool, UK Abstract Vascular injuries resulting from closed fractures of the humerus are rare. We describe two patients who developed unsuspected pseudoaneurysms following closed humeral fracture. Both patients pre- sented with a mass, suspicious for malignancy. In each case, diagnosis was made by magnetic resonance imaging. Keywords Pseudoaneurysm · Humerus · Fracture · Magnetic resonance imaging Skeletal Radiol (2001) 30:648–651 DOI 10.1007/s002560100421 CASE REPORT O. Harris C. J. Roche W. C. Torreggiani D. A. Ritchie M. Jane R. McWilliams P. L. Munk Delayed presentation of pseudoaneurysm complicating closed humeral fracture: MR diagnosis O. Harris Department of Radiology, Whiston Hospital, Prescot, Merseyside, Liverpool, L35 5DR, UK