A 61-year-old man presented with a painful mass in the right axilla that had been present for several months. Over the past few weeks, it had grown in size and his level of discomfort had increased dramatically. The patient denied fevers, redness, recent travel, insect bites, or similar symptoms in the past. He denied any history of recent or remote trauma to the right axilla, recent use of crutches, or other possible injury. He had no history of ischemic arm symptoms. On examination, a large pulsatile and tender mass was appreciated without surrounding erythema or induration (A). All extremity pulses were palpable, and there were no ischemic, neurologic, or edematous signs in the arm. An axillary duplex scan demonstrated a mass of 15 cm in its widest diameter and turbulent pulsatile flow within the mass. Arteriography confirmed the presence of a giant aneurysm of right lateral thoracic artery (Cover). Surgical treatment was recommended. The origin of the aneurysmal branch was ligated at its junction with the axillary artery through a deltopectoral-subclavicular approach, and then the aneurysm was excised (B). No sign of infection was encountered during exploration and histopathology of the aneurysmal mural specimen revealed only atherosclerosis (C). The patient was discharged without complication after postoperative 5 days. He remained problem-free at the 1-year follow-up. Degenerative, sometimes termed atherosclerotic, aneurysms of the axillary artery and its branches are rare. Pseudoaneurysms represent the majority of the reported aneurysms in this location, and they almost always occur as a result of trauma or instrumentation. 1,2 True aneurysm of the axillary artery or its branches can cause vascular or neurologic compression complications, thromboembolic events, or rupture, so they should be treated. Although endovascular options could be considered, in this case the large size and associated symptoms required decompression and open surgical treatment was effective.