Arterial pseudoaneurysms of the shoulder mimicking other entities: utilization of pulsation artifact on musculoskeletal MR for accurate diagnosis in 2 cases

We present two cases of pseudoaneurysm (PSA) about the shoulder mimicking more common clinical entities—soft tissue neoplasm and septic arthritis—for which biopsy of the mass and joint aspiration were requested respectively. We review the imaging findings of PSA with emphasis on findings in musculoskeletal protocol MRI, including the identification of pulsation artifact in both cases, which was critical to establishing the correct diagnosis. In the proper clinical setting, with imaging findings demonstrating a complex mass or fluid collection, MR images should be scrutinized for the presence of pulsation artifact, which can help diagnose a high-flow vascular lesion and avoid a potentially harmful invasive procedure such as biopsy.