Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 52 3 2014 03 15 234 237 EN Darioush M. Barzi Department of Orthopedic Surgery, Mostafa Hospital, Shahed University, Tehran, Iran. Sam H. Sami Department of Orthopedic Surgery, Shafa Hospital, Tehran University of Medical Sciences, Tehran, Iran. Ehsan Fallah Department of Orthopedic Surgery, Emam Reza Hospital, Army University, Tehran, Iran. 2015 10 11 A pseudo aneurysm results from leakage of blood from an artery after trauma or dehiscence or separation of a surgical anastomosis. The reported rate of pseudo aneurysm in access sites range from 0.88% to 8%. It has some cause like penetrating trauma, blunt trauma and endovascular procedure. The differential diagnoses of this lesion are hematoma, AV fistula, lymphadenopathy, lymphocele, DVT, compartment syndrome, soft tissue tumor. A 16 years old male was referred to our clinic with progressive swelling in his right leg for the past three month. In primary survey (MRI, CT, Bone Scan) patient was diagnosed with soft tissue tumor, but after biopsy and angiography he was diagnosed with pseudo aneurysm of anterior tibialis artery. Despite easy diagnosis of p aneurysm in most cases, the signs and symptoms are more likely to soft tissue mass in rare cases. So pseudo aneurysm should always be considered as one differential diagnosis for soft tissue tumors. https://acta.tums.ac.ir/index.php/acta/article/view/4663 https://acta.tums.ac.ir/index.php/acta/article/download/4663/4340